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{{Short description|1990 robotic space probe; studied the Sun from a near-polar orbit}}
{{Short description|NASA/ESA heliophysics mission (1990–2009)}}
{{More citations needed|date=February 2019}}
{{italic title}}
{{italic title}}
{{Use British English|date=June 2021}}
{{Use British English|date=June 2021}}
{{Use dmy dates|date=June 2021}}
{{Use dmy dates|date=June 2021}}
{{Distinguish|text=the 2024 lunar landing mission [[IM-1]], which used a spacecraft known as ''Odysseus''}}
{{Infobox spaceflight
{{Infobox spaceflight
| name = ''Ulysses''
| name = ''Ulysses''
| names_list = Odysseus
| names_list = Odysseus
| image = Ulysses spacecraft.jpg
| image = Ulysses spacecraft.jpg
| image_caption = ''Ulysses'' spacecraft
| image_caption = The ''Ulysses'' spacecraft being tested in [[European Space Research and Technology Centre|ESTEC]], Netherlands around 1985
| image_size = 300px
| image_size = 300px


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| COSPAR_ID = 1990-090B
| COSPAR_ID = 1990-090B
| SATCAT = 20842
| SATCAT = 20842
| website = [https://web.archive.org/web/20031226150122/http://solarsystem.nasa.gov/missions/profile.cfm?MCode=Ulysses NASA Page]<br/>[https://www.esa.int/esaSC/120395_index_0_m.html ESA Page]
| website = [https://web.archive.org/web/20031226150122/http://solarsystem.nasa.gov/missions/profile.cfm?MCode=Ulysses NASA Page]<br />[https://www.esa.int/esaSC/120395_index_0_m.html ESA Page]
| mission_duration = {{time interval|6 Oct 1990|30 Jun 2009}}<ref>{{cite web|url=https://solarsystem.nasa.gov/missions/ulysses/in-depth/ |title=Ulysses |publisher=NASA's Solar System Exploration website |access-date=September 25, 2023}}</ref>
| mission_duration = {{Age in years, months and days|1990|10|06|2023|9|7}} (in orbit)


| manufacturer = [[Astrium]] GmbH, [[Friedrichshafen]]<br />(formerly [[Dornier Flugzeugwerke|Dornier Systems]])
| spacecraft_bus =
| launch_mass = {{cvt|371|kg|lb}}<ref name=nasa1/>
| manufacturer = Astrium GmbH, [[Friedrichshafen]]<br/>(formerly [[Dornier Flugzeugwerke|Dornier Systems]])
| payload_mass = {{cvt|55|kg|lb}}
| launch_mass = {{cvt|371|kg}}<ref name="Ulysses">{{cite web|url=https://solarsystem.nasa.gov/missions/ulysses/in-depth/ |title=Ulysses |publisher=NASA's Solar System Exploration website |access-date=December 2, 2022}}</ref>
| dry_mass =
| dimensions = {{cvt|3.2|xx|3.3|xx|2.1|m|ft}}
| payload_mass = {{cvt|55|kg}}
| dimensions = {{cvt|3.2 × 3.3 × 2.1|m}}
| power = 285 [[watt]]s
| power = 285 [[watt]]s


| launch_date = 6 October 1990, 11:47:16 [[Coordinated Universal Time|UTC]]<ref name="Ulysses"></ref>
| launch_date = 6 October 1990, 11:47:16 [[Coordinated Universal Time|UTC]]<ref name=nasa1/>
| launch_rocket = [[Space Shuttle Discovery]] ([[STS-41]]) with [[Inertial Upper Stage]] and [[Payload Assist Module|PAM-S]]
| launch_rocket = {{OV|103}} <br /> [[STS-41]]/[[Inertial Upper Stage|IUS]]-[[Payload Assist Module|PAM-S]]
| launch_site = [[Kennedy Space Center]], [[Kennedy Space Center Launch Complex 39B|LC-39B]]
| launch_site = [[Kennedy Space Center|Kennedy]], [[Kennedy Space Center Launch Complex 39B|LC-39B]]
| launch_contractor = [[NASA]]
| launch_contractor = [[NASA]]


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| deactivated = 30 June 2009
| deactivated = 30 June 2009


| orbit_reference = [[Heliocentric orbit]]
| orbit_reference = [[Heliocentric orbit|Heliocentric]]
| orbit_periapsis = 1.35 AU
| orbit_periapsis = {{convert|1.35|AU|e6km|abbr=unit}}
| orbit_apoapsis = 5.40 AU
| orbit_apoapsis = {{convert|5.40|AU|e6km|abbr=unit}}
| orbit_inclination = 79.11°
| orbit_inclination = 79.11°
| orbit_period = 2,264.26 days (6.2 years)
| orbit_period = {{convert|2,264.26|day|year|abbr=off}}
| apsis = helion
| apsis = helion


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| object = [[Jupiter]] <small>(gravity assist)</small>
| object = [[Jupiter]] <small>(gravity assist)</small>
| arrival_date = 8 February 1992
| arrival_date = 8 February 1992
| distance = 440,439 km (6.3 Jupiter radii)
| distance = {{cvt|440439|km|mi}}
}}
}}


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}}
}}


'''''Ulysses''''' ({{IPAc-en|j|uː|ˈ|l|ɪ|s|iː|z}} {{respell|yoo|LISS|eez}}, {{IPAc-en|UKalso|ˈ|j|uː|l|ɪ|s|iː|z}} {{respell|YOO|liss|eez}}) was a [[Robotic spacecraft|robotic]] [[space probe]] whose primary mission was to orbit the [[Sun]] and study it at all latitudes. It was launched in 1990 and made three "fast latitude scans" of the Sun in 1994/1995, 2000/2001, and 2007/2008. In addition, the probe studied several comets. ''Ulysses'' was a joint venture of the [[European Space Agency]] (ESA) and the United States' [[NASA|National Aeronautics and Space Administration]] (NASA), under leadership of ESA with participation from Canada's [[National Research Council (Canada)|National Research Council]].<ref>{{cite web|quote=The Herzberg Institute of Astrophysics (HIA) of the National Research Council of Canada provided instrumentation and test equipment for the COsmic ray and Solar Particle INvestigation (COSPIN) on the ''Ulysses'' spacecraft. The COSPIN instrument consists of five sensors which measure energetic nucleons and electrons over a wide range of energies. This was the first participation by Canada in a deep-space interplanetary mission. |archive-url=https://web.archive.org/web/20110817205127/http://hiauly1.hia.nrc.ca/index.html|url=http://hiauly1.hia.nrc.ca/index.html|archive-date=August 17, 2011|title=Welcome to the HIA Ulysses Project |publisher=Herzberg Institute of Astrophysics}}</ref> The last day for mission operations on ''Ulysses'' was 30 June 2009.<ref name="ESA News"/><ref>[http://ulysses-ops.jpl.esa.int/ulsfct/the_odyssey_continues.html#12 The odyssey concludes ...] {{webarchive|url=https://web.archive.org/web/20120224180806/http://ulysses-ops.jpl.esa.int/ulsfct/the_odyssey_continues.html |date=February 24, 2012}}</ref>
'''''Ulysses''''' ({{IPAc-en|j|uː|ˈ|l|ɪ|s|iː|z}} {{respell|yoo|LISS|eez}}, {{IPAc-en|UKalso|ˈ|j|uː|l|ɪ|s|iː|z}} {{respell|YOO|liss|eez}}) was a [[Uncrewed spacecraft|robotic space probe]] whose primary mission was to orbit the [[Sun]] and study it at all latitudes. It was launched in 1990 and made three "fast latitude scans" of the Sun in 1994/1995, 2000/2001, and 2007/2008. In addition, the probe studied several comets. ''Ulysses'' was a joint venture of the [[European Space Agency]] (ESA) and the United States' [[NASA|National Aeronautics and Space Administration]] (NASA), under leadership of ESA with participation from Canada's [[National Research Council (Canada)|National Research Council]].<ref>{{cite web|quote=The Herzberg Institute of Astrophysics (HIA) of the National Research Council of Canada provided instrumentation and test equipment for the COsmic ray and Solar Particle INvestigation (COSPIN) on the ''Ulysses'' spacecraft. The COSPIN instrument consists of five sensors which measure energetic nucleons and electrons over a wide range of energies. This was the first participation by Canada in a deep-space interplanetary mission. |archive-url=https://web.archive.org/web/20110817205127/http://hiauly1.hia.nrc.ca/index.html|url=http://hiauly1.hia.nrc.ca/index.html|archive-date=August 17, 2011|title=Welcome to the HIA Ulysses Project |publisher=Herzberg Institute of Astrophysics}}</ref> The last day for mission operations on ''Ulysses'' was 30 June 2009.<ref name=esa-20090630/><ref>{{Cite web |title=The odyssey concludes... |url=http://ulysses-ops.jpl.esa.int/ulsfct/the_odyssey_continues.html |url-status=dead |archive-url=https://web.archive.org/web/20120224180806/http://ulysses-ops.jpl.esa.int/ulsfct/the_odyssey_continues.html |archive-date=February 24, 2012}}</ref>


To study the Sun at all latitudes, the probe needed to change its [[orbital inclination]] and leave the [[Ecliptic|plane of the Solar System]]. To change the orbital inclination of a spacecraft to about 80° requires a large change in heliocentric velocity, the energy to achieve which far exceeded the capabilities of any [[launch vehicle]]. To reach the desired orbit around the Sun, the mission's planners chose a [[gravity assist]] maneuver around [[Jupiter]], but this Jupiter encounter meant that ''Ulysses'' could not be powered by solar cells. The probe was powered instead by a [[radioisotope thermoelectric generator]] (RTG).
To study the Sun at all latitudes, the probe needed to change its [[orbital inclination]] and leave the [[Ecliptic|plane of the Solar System]]. To change the orbital inclination of a spacecraft to about 80° requires a large change in heliocentric velocity, the energy to achieve which far exceeded the capabilities of any [[launch vehicle]]. To reach the desired orbit around the Sun, the mission's planners chose a [[gravity assist]] maneuver around [[Jupiter]], but this Jupiter encounter meant that ''Ulysses'' could not be powered by solar cells. The probe was powered instead by a General Purpose Heat Source [[Radioisotope Thermoelectric Generator]] ([[GPHS-RTG]]).<ref>https://rps.nasa.gov/missions/13/ulysses/ {{Bare URL inline|date=August 2024}}</ref>


The [[spacecraft]] was originally named '''''Odysseus''''', because of its lengthy and indirect trajectory to study the solar poles. It was renamed ''Ulysses'', the [[Latin]] [[translation]] of "[[Odysseus]]", at ESA's request in honor not only of [[Homer]]'s mythological hero but also of [[Dante]]'s character in the [[Inferno (Dante)|''Inferno'']].<ref>"Inferno of Ulysses' urge to explore an uninhabited world behind the Sun. In ''Jane's Spaceflight Directory'' 1988, {{ISBN|0-7106-0860-8}}</ref> ''Ulysses'' was originally scheduled for launch in May 1986 aboard the [[Space Shuttle]] ''Challenger'' on [[STS-61-F]]. Due to the 28 January 1986 [[Space Shuttle Challenger disaster|loss of ''Challenger'']], the launch of ''Ulysses'' was delayed until 6 October 1990 aboard [[Space Shuttle Discovery|''Discovery'']] (mission [[STS-41]]).
The [[spacecraft]] was originally named '''''Odysseus''''', because of its lengthy and indirect trajectory to study the solar poles. It was renamed ''Ulysses'', the [[Latin]] [[translation]] of "[[Odysseus]]", at ESA's request in honor not only of [[Homer]]'s mythological hero but also of [[Dante]]'s character in the [[Inferno (Dante)|''Inferno'']].<ref>"Inferno of Ulysses' urge to explore an uninhabited world behind the Sun. In ''Jane's Spaceflight Directory'' 1988, {{ISBN|0-7106-0860-8}}</ref> ''Ulysses'' was originally scheduled for launch in May 1986 aboard the [[Space Shuttle]] ''Challenger'' on [[STS-61-F]]. Due to the 28 January 1986 [[Space Shuttle Challenger disaster|loss of ''Challenger'']], the launch of ''Ulysses'' was delayed until 6 October 1990 aboard [[Space Shuttle Discovery|''Discovery'']] (mission [[STS-41]]).
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The spacecraft was designed by ESA and built by [[Dornier Flugzeugwerke|Dornier Systems]], a German aircraft manufacturer. The body was roughly a box, approximately {{cvt|3.2 × 3.3 × 2.1|m}} in size. The box mounted the {{cvt|1.65|m}} [[dish antenna]] and the [[GPHS-RTG]] [[radioisotope thermoelectric generator]] (RTG) power source. The box was divided into noisy and quiet sections. The noisy section abutted the RTG; the quiet section housed the instrument electronics. Particularly "loud" components, such as the preamps for the radio dipole, were mounted outside the structure entirely, and the box acted as a [[Faraday cage]].
The spacecraft was designed by ESA and built by [[Dornier Flugzeugwerke|Dornier Systems]], a German aircraft manufacturer. The body was roughly a box, approximately {{cvt|3.2 × 3.3 × 2.1|m}} in size. The box mounted the {{cvt|1.65|m}} [[dish antenna]] and the [[GPHS-RTG]] [[radioisotope thermoelectric generator]] (RTG) power source. The box was divided into noisy and quiet sections. The noisy section abutted the RTG; the quiet section housed the instrument electronics. Particularly "loud" components, such as the preamps for the radio dipole, were mounted outside the structure entirely, and the box acted as a [[Faraday cage]].


''Ulysses'' was [[Spin-stabilisation|spin-stabilised]] about its z-axis which roughly coincides with the axis of the dish antenna. The RTG, [[whip antenna]]s, and instrument boom were placed to stabilize this axis, with the spin rate nominally at 5 [[Revolutions per minute|rpm]]. Inside the body was a [[hydrazine]] fuel tank. Hydrazine [[monopropellant]] was used for course corrections inbound to Jupiter, and later used exclusively to repoint the spin axis (and thus, the antenna) at Earth. The spacecraft was controlled by eight thrusters in two blocks. Thrusters were pulsed in the time domain to perform rotation or translation. Four sun sensors detected orientation. For fine attitude control, the S-band antenna feed was mounted slightly off-axis. This offset feed combined with the spacecraft spin introduced an apparent oscillation to a radio signal transmitted from Earth when received on board the spacecraft. The amplitude and phase of this oscillation were proportional to the orientation of the spin axis relative to the Earth direction. This method of determining the relative orientation is called [[conical scanning]] and was used by early radars for automated tracking of targets and was also very common in early infrared guided missiles.
''Ulysses'' was [[Spin-stabilisation|spin-stabilised]] about its z-axis which roughly coincides with the axis of the dish antenna. The RTG, [[whip antenna]]s, and instrument boom were placed to stabilize this axis, with the spin rate nominally at 5 [[Revolutions per minute|rpm]]. Inside the body was a [[hydrazine]] fuel tank. Hydrazine [[monopropellant]] was used for course corrections inbound to Jupiter, and later used exclusively to repoint the spin axis (and thus, the antenna) at Earth. The spacecraft was controlled by eight thrusters in two blocks. Thrusters were pulsed in the time domain to perform rotation or translation. Four [[Sun sensor]]s detected orientation. For fine attitude control, the S-band antenna feed was mounted slightly off-axis. This offset feed combined with the spacecraft spin introduced an apparent oscillation to a radio signal transmitted from Earth when received on board the spacecraft. The amplitude and phase of this oscillation were proportional to the orientation of the spin axis relative to the Earth direction. This method of determining the relative orientation is called [[conical scanning]] and was used by early radars for automated tracking of targets and was also very common in early infrared guided missiles.


The spacecraft used S-band for uplinked commands and downlinked telemetry, through dual redundant 5-watt transceivers. The spacecraft used [[X band|X-band]] for science return (downlink only), using dual 20 watts [[TWTA]]s until the failure of the last remaining TWTA in January 2008. Both bands used the dish antenna with prime-focus feeds, unlike the [[Cassegrain reflector|Cassegrain]] feeds of most other spacecraft dishes.
The spacecraft used S-band for uplinked commands and downlinked telemetry, through dual redundant 5-watt transceivers. The spacecraft used [[X band|X-band]] for science return (downlink only), using dual 20 watts [[TWTA]]s until the failure of the last remaining TWTA in January 2008. Both bands used the dish antenna with prime-focus feeds, unlike the [[Cassegrain reflector|Cassegrain]] feeds of most other spacecraft dishes.
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[[File:Ulysses radial boom test.jpg|thumb|upright=1.0|right|''Ulysses'' radial boom test]]
[[File:Ulysses radial boom test.jpg|thumb|upright=1.0|right|''Ulysses'' radial boom test]]


The twelve different Instruments came from ESA and NASA. The first design was based on two probes, one by NASA and one by ESA, but the probe of NASA was defunded and in the end the instruments of the cancelled probe were mounted on Ulyssses.<ref>{{cite web|title=Ulysses factsheet|url=http://www.esa.int/Science_Exploration/Space_Science/Ulysses_factsheet|access-date=2021-05-07|website=esa.int}}</ref>
The twelve different Instruments came from ESA and NASA. The first design was based on two probes, one by NASA and one by ESA, but the probe of NASA was defunded and in the end the instruments of the cancelled probe were mounted on ''Ulysses''.<ref>{{cite web|title=Ulysses factsheet|url=http://www.esa.int/Science_Exploration/Space_Science/Ulysses_factsheet|access-date=2021-05-07|website=esa.int}}</ref>


* '''Radio/Plasma antennas:''' Two [[beryllium copper]] antennas were unreeled outwards from the body, perpendicular to the RTG and spin axis. Together this [[Dipole antenna|dipole]] spanned 72 meters (236.2&nbsp;ft). A third antenna, of hollow beryllium copper, was deployed from the body, along the spin axis opposite the dish. It was a [[monopole antenna]], 7.5 meters (24.6&nbsp;ft) long. These measured radio waves generated by plasma releases, or the plasma itself as it passed over the spacecraft. This receiver ensemble was sensitive from DC to 1&nbsp;MHz.<ref>[http://ulysses.jpl.nasa.gov/spacecraft/inst_urap.html Unified Radio and Plasma Wave Investigation, JPL] {{Webarchive|url=https://web.archive.org/web/20090117094444/http://ulysses.jpl.nasa.gov/spacecraft/inst_urap.html |date=January 17, 2009 }}</ref>
* '''Radio/Plasma antennas:''' Two [[beryllium copper]] antennas were unreeled outwards from the body, perpendicular to the RTG and spin axis. Together this [[Dipole antenna|dipole]] spanned 72 meters (236.2&nbsp;ft). A third antenna, of hollow beryllium copper, was deployed from the body, along the spin axis opposite the dish. It was a [[monopole antenna]], 7.5 meters (24.6&nbsp;ft) long. These measured radio waves generated by plasma releases, or the plasma itself as it passed over the spacecraft. This receiver ensemble was sensitive from DC to 1&nbsp;MHz.<ref>[http://ulysses.jpl.nasa.gov/spacecraft/inst_urap.html Unified Radio and Plasma Wave Investigation, JPL] {{Webarchive|url=https://web.archive.org/web/20090117094444/http://ulysses.jpl.nasa.gov/spacecraft/inst_urap.html |date=January 17, 2009 }}</ref>
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* Lastly, the radio communications link could be used to search for [[gravitational waves]]<ref>[http://www.sp.ph.ic.ac.uk/~giacomo/Papers/1992AAS.pdf The Gravity Wave Experiment, Astronomy and Astrophysics] {{Webarchive|url=https://web.archive.org/web/20081219053444/http://www.sp.ph.ic.ac.uk/~giacomo/Papers/1992AAS.pdf |date=December 19, 2008 }}</ref> (through [[Doppler shift]]s) and to probe the Sun's atmosphere through [[radio occultation]]. No gravitational waves were detected.
* Lastly, the radio communications link could be used to search for [[gravitational waves]]<ref>[http://www.sp.ph.ic.ac.uk/~giacomo/Papers/1992AAS.pdf The Gravity Wave Experiment, Astronomy and Astrophysics] {{Webarchive|url=https://web.archive.org/web/20081219053444/http://www.sp.ph.ic.ac.uk/~giacomo/Papers/1992AAS.pdf |date=December 19, 2008 }}</ref> (through [[Doppler shift]]s) and to probe the Sun's atmosphere through [[radio occultation]]. No gravitational waves were detected.
* Total instrument mass was 55&nbsp;kg.
* Total instrument mass was 55&nbsp;kg.
* '''Magnetometer (MAG):''' MAG measured the magnetic field in the heliosphere. Measurements of Jupiter's magnetic field were also performed. Two [[magnetometer]]s performed Ulysses' magnetic field measurements, the Vector Helium Magnetometer and the Fluxgate Magnetometer.<ref>{{cite journal |title=The magnetic field investigation on the ULYSSES mission - Instrumentation and preliminary scientific results |journal=Astronomy & Astrophysics Supplement Series |date=20 August 1991 |volume=91 |issue=2 |pages=221-236 |url=https://adsabs.harvard.edu/full/1992A%26AS...92..221B}}</ref>
* '''Magnetometer (MAG):''' MAG measured the magnetic field in the heliosphere. Measurements of Jupiter's magnetic field were also performed. Two [[magnetometer]]s performed ''Ulysses''{{'}} magnetic field measurements, the Vector Helium Magnetometer and the Fluxgate Magnetometer.<ref>{{cite journal |title=The magnetic field investigation on the ULYSSES mission - Instrumentation and preliminary scientific results |journal=Astronomy & Astrophysics Supplement Series |date=20 August 1991 |volume=91 |issue=2 |pages=221–236 |bibcode=1992A&AS...92..221B |url=https://adsabs.harvard.edu/full/1992A%26AS...92..221B |last1=Balogh |first1=A. |last2=Beek |first2=T. J. |last3=Forsyth |first3=R. J. |last4=Hedgecock |first4=P. C. |last5=Marquedant |first5=R. J. |last6=Smith |first6=E. J. |last7=Southwood |first7=D. J. |last8=Tsurutani |first8=B. T. }}</ref>
* '''Solar Wind Plasma Experiment (SWOOPS):''' detected the solar wind at all solar distances and latitudes and in three dimensions. It measured positive ions and electrons.<ref>Goldstein, Bruce. [http://helio.estec.esa.nl/ulysses/archive/swoops_bae_un.html SWOOPS/Electron{{spaced ndash}}User Notes] {{Webarchive|url=https://web.archive.org/web/20060927051549/http://helio.estec.esa.nl/ulysses/archive/swoops_bae_un.html |date=September 27, 2006 }}, [[Jet Propulsion Laboratory]]</ref>
* '''Solar Wind Plasma Experiment (SWOOPS):''' detected the solar wind at all solar distances and latitudes and in three dimensions. It measured positive ions and electrons.<ref>Goldstein, Bruce. [http://helio.estec.esa.nl/ulysses/archive/swoops_bae_un.html SWOOPS/Electron{{spaced ndash}}User Notes] {{Webarchive|url=https://web.archive.org/web/20060927051549/http://helio.estec.esa.nl/ulysses/archive/swoops_bae_un.html |date=September 27, 2006 }}, [[Jet Propulsion Laboratory]]</ref>
* '''Solar Wind Ion Composition Instrument (SWICS):''' determined composition, temperature and speed of the atoms and ions that comprise the solar wind.<ref>{{Cite journal|last1=Geiss|first1=J|last2=Gloeckler|first2=G|last3=von Steiger|first3=R|last4=Balsiger|first4=H|last5=Fisk|first5=L.|last6=Galvin|first6=A.|author-link6=Antoinette Galvin|last7=Ipavich|first7=F.|last8=Livi|first8=S|last9=McKenzie|first9=J.|last10=Ogilvie|first10=K.|last11=et|first11=al.|date=1995-05-19|title=The southern high-speed stream: results from the SWICS instrument on Ulysses|url=https://www.science.org/doi/10.1126/science.7754380|journal=Science|language=en|volume=268|issue=5213|pages=1033–1036|doi=10.1126/science.7754380|pmid=7754380|bibcode=1995Sci...268.1033G|issn=0036-8075}}</ref><ref>{{Cite journal|last1=von Steiger|first1=R.|last2=Geiss|first2=J.|last3=Gloeckler|first3=G.|last4=Galvin|first4=A. B.|author-link4=Antoinette Galvin|date=1995-04-01|title=Kinetic properties of heavy ions in the solar wind from SWICS/Ulysses|url=https://doi.org/10.1007/BF00768756|journal=Space Science Reviews|language=en|volume=72|issue=1|pages=71–76|doi=10.1007/BF00768756|bibcode=1995SSRv...72...71V|s2cid=189797680|issn=1572-9672}}</ref>
* '''Solar Wind Ion Composition Instrument (SWICS):''' determined composition, temperature and speed of the atoms and ions that comprise the solar wind.<ref>{{Cite journal|last1=Geiss|first1=J|last2=Gloeckler|first2=G|last3=von Steiger|first3=R|last4=Balsiger|first4=H|last5=Fisk|first5=L.|last6=Galvin|first6=A.|author-link6=Antoinette Galvin|last7=Ipavich|first7=F.|last8=Livi|first8=S|last9=McKenzie|first9=J.|last10=Ogilvie|first10=K.|last11=et|first11=al.|date=1995-05-19|title=The southern high-speed stream: results from the SWICS instrument on Ulysses|url=https://www.science.org/doi/10.1126/science.7754380|journal=Science|language=en|volume=268|issue=5213|pages=1033–1036|doi=10.1126/science.7754380|pmid=7754380|bibcode=1995Sci...268.1033G|issn=0036-8075}}</ref><ref>{{Cite journal|last1=von Steiger|first1=R.|last2=Geiss|first2=J.|last3=Gloeckler|first3=G.|last4=Galvin|first4=A. B.|author-link4=Antoinette Galvin|date=1995-04-01|title=Kinetic properties of heavy ions in the solar wind from SWICS/Ulysses|url=https://doi.org/10.1007/BF00768756|journal=Space Science Reviews|language=en|volume=72|issue=1|pages=71–76|doi=10.1007/BF00768756|bibcode=1995SSRv...72...71V|s2cid=189797680|issn=1572-9672}}</ref>
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[[File:Ulysses sits atop the PAM-S and IUS combination.jpg|thumb|upright=1.0|left|''Ulysses'' sits atop the PAM-S and IUS combination]]
[[File:Ulysses sits atop the PAM-S and IUS combination.jpg|thumb|upright=1.0|left|''Ulysses'' sits atop the PAM-S and IUS combination]]
[[File:Artist picture-Ulysses after deployment.jpg|thumb|upright=1.0|right|Illustration of ''Ulysses'' after deployment]]
[[File:Artist picture-Ulysses after deployment.jpg|thumb|upright=1.0|right|Illustration of ''Ulysses'' after deployment]]
[[File:Artist's conception of NASA solar polar spacecraft.jpg|thumb|upright=1.0|right|Illustration of Solar Polar on IUS]]
[[File:Artist's conception of NASA solar polar spacecraft.jpg|thumb|upright=1.0|right|Illustration of the ''International Solar Polar Mission'' on IUS]]


Until ''Ulysses'', the Sun had only been observed from low solar latitudes. The Earth's orbit defines the [[ecliptic]] plane, which differs from the Sun's equatorial plane by only 7.25°. Even spacecraft directly orbiting the Sun do so in planes close to the ecliptic because a direct launch into a high-inclination solar orbit would require a prohibitively large launch vehicle.
Until ''Ulysses'', the Sun had only been observed from low solar latitudes. The Earth's orbit defines the [[ecliptic]] plane, which differs from the Sun's equatorial plane by only 7.25°. Even spacecraft directly orbiting the Sun do so in planes close to the ecliptic because a direct launch into a high-inclination solar orbit would require a prohibitively large launch vehicle.
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Originally, two spacecraft were to be built by NASA and ESA, as the '''International Solar Polar Mission.''' One would be sent over Jupiter, then under the Sun. The other would fly under Jupiter, then over the Sun. This would provide simultaneous coverage. Due to cutbacks, the U.S. spacecraft was cancelled in 1981. One spacecraft was designed, and the project recast as ''Ulysses,'' due to the indirect and untried flight path. NASA would provide the Radioisotope Thermoelectric Generator (RTG) and launch services, ESA would build the spacecraft assigned to Astrium GmbH, [[Friedrichshafen]], [[Germany]] (formerly Dornier Systems). The instruments would be split into teams from universities and research institutes in Europe and the United States. This process provided the 12 instruments on board.
Originally, two spacecraft were to be built by NASA and ESA, as the '''International Solar Polar Mission.''' One would be sent over Jupiter, then under the Sun. The other would fly under Jupiter, then over the Sun. This would provide simultaneous coverage. Due to cutbacks, the U.S. spacecraft was cancelled in 1981. One spacecraft was designed, and the project recast as ''Ulysses,'' due to the indirect and untried flight path. NASA would provide the Radioisotope Thermoelectric Generator (RTG) and launch services, ESA would build the spacecraft assigned to Astrium GmbH, [[Friedrichshafen]], [[Germany]] (formerly Dornier Systems). The instruments would be split into teams from universities and research institutes in Europe and the United States. This process provided the 12 instruments on board.


The changes delayed launch from February 1983 to May 1986 when it was to be deployed by the [[Space Shuttle Challenger|Space Shuttle ''Challenger'']] (boosted by the proposed [[Centaur G Prime]] upper stage. However, the [[Space Shuttle Challenger disaster|''Challenger'' disaster]] forced a two-and-a-half year stand down of the shuttle fleet, mandated the cancellation of the Centaur-G upper stage, and pushed the launch date to October 1990.<ref>[https://arstechnica.com/science/2015/10/dispatches-from-the-death-star-the-rise-and-fall-of-nasas-shuttle-centaur/ A Deathblow to the Death Star: The Rise and Fall of NASA's Shuttle-Centaur, ArsTechnica, October 2015]</ref>
The changes delayed launch from February 1983 to May 1986 when it was to be deployed by the [[Space Shuttle Challenger|Space Shuttle ''Challenger'']] (boosted by the proposed [[Centaur G Prime]] upper stage). However, the [[Space Shuttle Challenger disaster|''Challenger'' disaster]] forced a two-and-a-half year stand down of the shuttle fleet, mandated the cancellation of the Centaur-G upper stage, and pushed the launch date to October 1990.<ref name=arstech1/>


=== Launch ===
=== Launch ===
[[File:STS-41 Ulysses deployment.jpg|thumb|upright=1.0|right|''Ulysses'' after deployment from [[STS-41]]]]
[[File:STS-41 Ulysses deployment.jpg|thumb|upright=1.0|right|''Ulysses'' after deployment from [[STS-41]]]]


''Ulysses'' was deployed into low Earth orbit from the Space Shuttle ''Discovery''. From there, it was propelled on a trajectory to Jupiter by a combination of solid rocket motors.<ref>[http://www.esa.int/esaSC/SEMTDTUG3HF_index_0.html ESA—Space Science—Sun to set on Ulysses solar mission on 1 July]</ref> This upper stage consisted of a two-stage [[Boeing]] [[Inertial Upper Stage|IUS]] (Inertial Upper Stage), plus a [[McDonnell Douglas]] PAM-S ([[Payload Assist Module]]-Special). The IUS was inertially stabilised and actively guided during its burn. The PAM-S was unguided and it and ''Ulysses'' were spun up to 80 rpm for stability at the start of its burn. On burnout of the PAM-S, the motor and spacecraft stack was [[yo-yo de-spin|yo-yo de-spun]] (weights deployed at the end of cables) to below 8 rpm prior to separation of the spacecraft. On leaving Earth, the spacecraft became the fastest ever artificially-accelerated spacecraft, and held that title until the ''[[New Horizons]]'' probe was launched.
''Ulysses'' was deployed into low Earth orbit from the Space Shuttle ''Discovery''. From there, it was propelled on a trajectory to Jupiter by a combination of solid rocket motors.<ref name=esa-20080612/> This upper stage consisted of a two-stage [[Boeing]] [[Inertial Upper Stage|IUS]] (Inertial Upper Stage), plus a [[McDonnell Douglas]] PAM-S ([[Payload Assist Module]]-Special). The IUS was inertially stabilised and actively guided during its burn. The PAM-S was unguided and it and ''Ulysses'' were spun up to 80 rpm for stability at the start of its burn. On burnout of the PAM-S, the motor and spacecraft stack was [[yo-yo de-spin|yo-yo de-spun]] (weights deployed at the end of cables) to below 8 rpm prior to separation of the spacecraft. On leaving Earth, the spacecraft became the fastest ever artificially-accelerated spacecraft, and held that title until the ''[[New Horizons]]'' probe was launched.


On its way to Jupiter, the spacecraft was in an elliptical non-[[Hohmann transfer orbit]]. At this time, ''Ulysses'' had a low orbital inclination to the ecliptic.
On its way to Jupiter, the spacecraft was in an elliptical non-[[Hohmann transfer orbit]]. At this time, ''Ulysses'' had a low orbital inclination to the ecliptic.


=== Jupiter swing-by ===
=== Jupiter swing-by ===
[[File:Ulysses 2 orbit.jpg|thumb|upright=1.0|right|''Ulysses''{{'}} second orbit (1999–2004)]]
{{Unreferenced section|date=June 2024}}[[File:Ulysses 2 orbit.jpg|thumb|upright=1.0|right|''Ulysses''{{'}} second orbit (1999–2004)]]
[[File:Animation of Ulysses trajectory.gif|thumb|upright=1.0|right|Animation of ''Ulysses''{{'s}} trajectory from 6 October 1990 to 29 June 2009<br/>{{legend2|magenta| ''Ulysses'' }}{{·}}{{legend2|Royalblue|[[Earth]]}}{{·}}{{legend2|Gold|[[Jupiter]]}} {{·}}{{legend2| Cyan |[[C/2006 P1]]}}{{·}}{{legend2| Lime |[[C/1996 B2]] }}{{·}}{{legend2| OrangeRed |[[C/1999 T1]] }}]]
[[File:Animation of Ulysses trajectory.gif|thumb|upright=1.0|right|Animation of ''Ulysses''{{'s}} trajectory from 6 October 1990 to 29 June 2009<br />{{legend2|magenta| ''Ulysses'' }}{{·}}{{legend2|Royalblue|[[Earth]]}}{{·}}{{legend2|Gold|[[Jupiter]]}} {{·}}{{legend2| Cyan |[[C/2006 P1]]}}{{·}}{{legend2| Lime |[[C/1996 B2]] }}{{·}}{{legend2| OrangeRed |[[C/1999 T1]] }}]]


It arrived at Jupiter on 8 February 1992 for a [[swing-by maneuver]] that increased its inclination to the [[ecliptic]] by 80.2°. The giant planet's gravity bent the spacecraft's flight path southward and away from the ecliptic plane. This put it into a final orbit around the Sun that would take it past the Sun's north and south poles. The size and shape of the orbit were adjusted to a much smaller degree so that aphelion remained at approximately 5 AU, Jupiter's distance from the Sun, and perihelion was somewhat greater than 1 AU, the Earth's distance from the Sun. The orbital period is approximately six years.
It arrived at Jupiter on 8 February 1992 for a [[swing-by maneuver]] that increased its inclination to the [[ecliptic]] by 80.2°. The giant planet's gravity bent the spacecraft's flight path southward and away from the ecliptic plane. This put it into a final orbit around the Sun that would take it past the Sun's north and south poles. The size and shape of the orbit were adjusted to a much smaller degree so that aphelion remained at approximately 5 AU, Jupiter's distance from the Sun, and perihelion was somewhat greater than 1 AU, the Earth's distance from the Sun. The orbital period is approximately six years.


=== Polar regions of the Sun ===
=== Polar regions of the Sun ===
{{Unreferenced section|date=June 2024}}
Between 1994 and 1995 it explored both the southern and [[north]]ern polar regions of the Sun, respectively.
Between 1994 and 1995 it explored both the southern and [[north]]ern polar regions of the Sun, respectively.


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=== Comet C/1999 T1 (McNaught–Hartley) ===
=== Comet C/1999 T1 (McNaught–Hartley) ===
An encounter with a comet tail happened again in 2004<ref>{{cite book|url=https://books.google.com/books?id=Sh7UBwAAQBAJ|title=The Sun and the Heliosphere as an Integrated System|isbn=9781402028311|last1=Poletto |first1=Giannina|last2=Suess|first2=Steve T.|date=5 June 2013|publisher=Springer }}</ref> when ''Ulysses'' flew through the ion tailings of [[C/1999 T1]] (McNaught-Hartley). A [[coronal mass ejection]] carried the cometary material to ''Ulysses''.<ref name="esa-tail">[http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=34612 Ulysses Catches Another Comet by the Tail]</ref><ref name="tail-Gloeckler">[http://www.iop.org/EJ/article/1538-4357/604/2/L121/18096.html G. Gloeckler et al. Cometary Ions Trapped in a Coronal Mass Ejection]</ref>
An encounter with a comet tail happened again in 2004<ref>{{cite book|url=https://books.google.com/books?id=Sh7UBwAAQBAJ|title=The Sun and the Heliosphere as an Integrated System|isbn=9781402028311|last1=Poletto |first1=Giannina|last2=Suess|first2=Steve T.|date=5 June 2013|publisher=Springer }}</ref> when ''Ulysses'' flew through the ion tailings of [[C/1999 T1 (McNaught-Hartley)]]. A [[coronal mass ejection]] carried the cometary material to ''Ulysses''.<ref name="esa-tail">{{Cite web |title=Ulysses Catches Another Comet by the Tail |url=https://sci.esa.int/web/ulysses/-/34612-ulysses-catches-another-comet-by-the-tail |access-date=2024-06-22 |website=sci.esa.int}}</ref><ref name=Gloeckler_2004/>


=== Second Jupiter encounter ===
=== Second Jupiter encounter ===
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[[File:Ulysses RTG.jpg|thumb|upright=1.0|right|''Ulysses'' [[Radioisotope thermoelectric generator]]]]
[[File:Ulysses RTG.jpg|thumb|upright=1.0|right|''Ulysses'' [[Radioisotope thermoelectric generator]]]]


ESA's Science Program Committee approved the fourth extension of the ''Ulysses'' mission to March 2004 <ref>[http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=34647 ESA Science & Technology: Ulysses Mission Extended]</ref> thereby allowing it to operate over the Sun's poles for the third time in 2007 and 2008. After it became clear that the power output from the spacecraft's RTG would be insufficient to operate science instruments and keep the [[Spacecraft attitude control|attitude control]] fuel, [[hydrazine]], from freezing, instrument power sharing was initiated. Up until then, the most important instruments had been kept online constantly, whilst others were deactivated. When the probe neared the Sun, its power-hungry heaters were turned off and all instruments were turned on.<ref>[http://www.esa.int/esaCP/SEMUHTN2UXE_index_0.html ESA Portal - Ulysses scores a hat-trick]</ref>
ESA's Science Program Committee approved the fourth extension of the ''Ulysses'' mission to March 2004 <ref>[http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=34647 ESA Science & Technology: Ulysses Mission Extended]</ref> thereby allowing it to operate over the Sun's poles for the third time in 2007 and 2008. After it became clear that the power output from the spacecraft's RTG would be insufficient to operate science instruments and keep the [[Spacecraft attitude control|attitude control]] fuel, [[hydrazine]], from freezing, instrument power sharing was initiated. Up until then, the most important instruments had been kept online constantly, whilst others were deactivated. When the probe neared the Sun, its power-hungry heaters were turned off and all instruments were turned on.<ref>{{Cite web |title=Ulysses scores a hat-trick |url=https://www.esa.int/Science_Exploration/Space_Science/Ulysses_scores_a_hat-trick |access-date=2024-06-22 |website=www.esa.int |language=en}}</ref>


On 22 February 2008, 17 years and 4 months after the launch of the spacecraft, [[European Space Agency|ESA]] and [[NASA]] announced that the mission operations for ''Ulysses'' would likely cease within a few months.<ref>{{cite web|url=http://www.esa.int/esaCP/SEM6UE3CXCF_index_0.html|title=Ulysses mission coming to a natural end|date=February 22, 2008|access-date=February 23, 2008|publisher=European Space Agency}}</ref><ref>{{cite news|url=http://www.nasa.gov/topics/solarsystem/features/ulysses-20080222.html|title=International Solar Mission to End Following Stellar Performance|access-date=February 23, 2008 |date=February 22, 2008|publisher=NASA}} {{PD-notice}}</ref> On 12 April 2008, NASA announced that the end date will be 1 July 2008.<ref>{{Cite web |url=https://news.yahoo.com/s/ap/20080612/ap_on_sc/sci_solar_probe |title=RIP: Ulysses solar probe coming to end soon - Yahoo! News |access-date=15 January 2017 |archive-date=17 June 2008 |archive-url=https://web.archive.org/web/20080617110614/http://news.yahoo.com/s/ap/20080612/ap_on_sc/sci_solar_probe |url-status=dead }}</ref>
On 22 February 2008, 17 years and 4 months after the launch of the spacecraft, [[European Space Agency|ESA]] and [[NASA]] announced that the mission operations for ''Ulysses'' would likely cease within a few months.<ref>{{cite web|url=http://www.esa.int/esaCP/SEM6UE3CXCF_index_0.html|title=Ulysses mission coming to a natural end|date=February 22, 2008|access-date=February 23, 2008|publisher=European Space Agency}}</ref><ref>{{cite news|url=http://www.nasa.gov/topics/solarsystem/features/ulysses-20080222.html|title=International Solar Mission to End Following Stellar Performance|access-date=February 23, 2008 |date=February 22, 2008|publisher=NASA}} {{PD-notice}}</ref> On 12 April 2008, NASA announced that the end date will be 1 July 2008.<ref>{{Cite web |url=https://news.yahoo.com/s/ap/20080612/ap_on_sc/sci_solar_probe |title=RIP: Ulysses solar probe coming to end soon - Yahoo! News |access-date=15 January 2017 |archive-date=17 June 2008 |archive-url=https://web.archive.org/web/20080617110614/http://news.yahoo.com/s/ap/20080612/ap_on_sc/sci_solar_probe |url-status=dead }}</ref>


The spacecraft operated successfully for over four times its [[design life]]. A component within the last remaining working chain of [[X band|X-band]] downlink subsystem failed on 15 January 2008. The other chain in the X-band subsystem had previously failed in 2003.<ref>{{cite web|url=http://ulysses-ops.jpl.esa.int/ulsfct/opsfiles/03feb_ops.html|title=February 2003 Operations|publisher=European Space Agency|url-status=dead|archive-url=https://web.archive.org/web/20090703055833/http://ulysses-ops.jpl.esa.int/ulsfct/opsfiles/03feb_ops.html|archive-date=July 3, 2009}}</ref>
The spacecraft operated successfully for over four times its [[design life]]. A component within the last remaining working chain of [[X band|X-band]] downlink subsystem failed on 15 January 2008. The other chain in the X-band subsystem had previously failed in 2003.<ref name=ulysses.ops-1/>


[[Downlink]] to [[Earth]] resumed on [[S band|S-band]], but the [[beamwidth]] of the [[high gain antenna]] in the S-band was not as narrow as in the X–band, so that the received downlink signal was much weaker, hence reducing the achievable [[bit rate|data rate]]. As the spacecraft traveled on its outbound [[trajectory]] to the orbit of Jupiter, the downlink signal would have eventually fallen below the receiving capability of even the largest antennas (70 meters - 229.7 feet - in diameter) of the [[Deep Space Network]].
[[Downlink]] to [[Earth]] resumed on [[S band|S-band]], but the [[beamwidth]] of the [[high gain antenna]] in the S-band was not as narrow as in the X–band, so that the received downlink signal was much weaker, hence reducing the achievable [[bit rate|data rate]]. As the spacecraft traveled on its outbound [[trajectory]] to the orbit of Jupiter, the downlink signal would have eventually fallen below the receiving capability of even the largest antennas (70 meters - 229.7 feet - in diameter) of the [[Deep Space Network]].
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Even before the downlink signal was lost due to distance, the [[hydrazine]] attitude control fuel on board the spacecraft was considered likely to [[freezing|freeze]], as the [[radioisotope thermal generators]] (RTGs) failed to generate enough power for the heaters to overcome radiative heat loss into space. Once the hydrazine froze, the spacecraft would no longer be able to maneuver to keep its high gain antenna pointing towards Earth, and the downlink signal would then be lost in a matter of days. The failure of the X-band communications subsystem hastened this, because the coldest part of the fuel pipework was routed over the X-band [[TWTA|traveling-wave tube amplifier]]s, because they generated enough heat during operation to keep the propellant plumbing warm.
Even before the downlink signal was lost due to distance, the [[hydrazine]] attitude control fuel on board the spacecraft was considered likely to [[freezing|freeze]], as the [[radioisotope thermal generators]] (RTGs) failed to generate enough power for the heaters to overcome radiative heat loss into space. Once the hydrazine froze, the spacecraft would no longer be able to maneuver to keep its high gain antenna pointing towards Earth, and the downlink signal would then be lost in a matter of days. The failure of the X-band communications subsystem hastened this, because the coldest part of the fuel pipework was routed over the X-band [[TWTA|traveling-wave tube amplifier]]s, because they generated enough heat during operation to keep the propellant plumbing warm.


The previously announced mission end date of 1 July 2008, came and went but mission operations continued albeit in a reduced capacity. The availability of science data gathering was limited to only when ''Ulysses'' was in contact with a ground station due to the deteriorating S-band downlink margin no longer being able to support simultaneous real-time data and tape recorder playback.<ref>[http://ulysses-ops.jpl.esa.int/ulsfct/opsfiles/08may_ops.html#max-512bps Ulysses Mission Ops—No more data playback] {{Webarchive|url=https://web.archive.org/web/20081202042239/http://ulysses-ops.jpl.esa.int/ulsfct/opsfiles/08may_ops.html#max-512bps|date=December 2, 2008}}</ref> When the spacecraft was out of contact with a ground station, the S-band transmitter was switched off and the power was diverted to the internal heaters to add to the warming of the hydrazine. On 30 June 2009, ground controllers sent commands to switch to the low gain antennas. This stopped communications with the spacecraft, in combination with previous commands to shut down its transmitter entirely.<ref name="ESA News">{{cite web|url=http://www.esa.int/esaCP/SEMWHF1P0WF_index_0.html|title=Ulysses: 12 extra months of valuable science |date=June 30, 2009|publisher=European Space Agency|access-date=July 1, 2009}}</ref><ref name="NASA JPL">{{cite web|url=http://www.jpl.nasa.gov/news/news.cfm?release=2009-104|title=Ulysses Spacecraft Ends Historic Mission of Discovery|website=[[Jet Propulsion Laboratory]]|date=June 30, 2009|access-date=July 1, 2009|archive-date=16 July 2009|archive-url=https://web.archive.org/web/20090716200317/http://www.jpl.nasa.gov/news/news.cfm?release=2009-104|url-status=dead}} {{PD-notice}}</ref>
The previously announced mission end date of 1 July 2008, came and went but mission operations continued albeit in a reduced capacity. The availability of science data gathering was limited to only when ''Ulysses'' was in contact with a ground station due to the deteriorating S-band downlink margin no longer being able to support simultaneous real-time data and tape recorder playback.<ref name=ulysses.ops-2/> When the spacecraft was out of contact with a ground station, the S-band transmitter was switched off and the power was diverted to the internal heaters to add to the warming of the hydrazine. On 30 June 2009, ground controllers sent commands to switch to the low gain antennas. This stopped communications with the spacecraft, in combination with previous commands to shut down its transmitter entirely.{{r|esa-20090630|nasa-20090630}}


== Results ==
== Results ==
[[File:STS-41 launch.jpg|thumb|upright=1.0|right|STS-41 launches from [[Kennedy Space Center]], 6 October 1990.]]
[[File:STS-41 launch.jpg|thumb|upright=1.0|right|STS-41 launches from [[Kennedy Space Center]], 6 October 1990.]]


During cruise phases, ''Ulysses'' provided unique data. As the only spacecraft out of the ecliptic with a [[Gamma ray|gamma-ray]] instrument, ''Ulysses'' was an important part of the [[InterPlanetary Network]] (IPN). The IPN detects [[gamma ray burst]]s (GRBs); since gamma rays cannot be focused with mirrors, it was very difficult to locate GRBs with enough accuracy to study them further. Instead, several spacecraft can locate the burst through [[multilateration]]. Each spacecraft has a gamma-ray detector, with readouts noted in tiny fractions of a second. By comparing the arrival times of gamma showers with the separations of the spacecraft, a location can be determined, for follow-up with other telescopes. Because gamma rays travel at the speed of light, wide separations are needed. Typically, a determination came from comparing: one of several spacecraft orbiting the Earth, an inner-Solar-system probe (to [[Mars]], [[Venus]], or an [[asteroid]]), and ''Ulysses''. When ''Ulysses'' crossed the ecliptic twice per orbit, many GRB determinations lost accuracy.
During cruise phases, ''Ulysses'' provided unique data. As the only spacecraft out of the ecliptic with a [[Gamma ray|gamma-ray]] instrument, ''Ulysses'' was an important part of the [[InterPlanetary Network]] (IPN). The IPN detects [[gamma ray burst]]s (GRBs); since gamma rays cannot be focused with mirrors, it was very difficult to locate GRBs with enough accuracy to study them further. Instead, several spacecraft can locate the burst through [[multilateration]]. Each spacecraft has a gamma-ray detector, with readouts noted in tiny fractions of a second. By comparing the arrival times of gamma showers with the separations of the spacecraft, a location can be determined, for follow-up with other telescopes. Because gamma rays travel at the speed of light, wide separations are needed. Typically, a determination came from comparing: one of several spacecraft orbiting the Earth, an inner-Solar-System probe (to [[Mars]], [[Venus]], or an [[asteroid]]), and ''Ulysses''. When ''Ulysses'' crossed the ecliptic twice per orbit, many GRB determinations lost accuracy.


Additional discoveries:{{r|nasa-20080612|nasa1}}
Additional discoveries:<ref>{{Cite web|last=|date=June 12, 2008|title=International Mission Studying Sun to Conclude|url=https://www.jpl.nasa.gov/news/international-mission-studying-sun-to-conclude|access-date=2021-08-01|website=NASA Jet Propulsion Laboratory (JPL)|language=en}}</ref><ref>{{Cite web|title=Missions: Ulysses|url=https://solarsystem.nasa.gov/missions/ulysses/in-depth/|access-date=August 1, 2021}}</ref>
* Data provided by ''Ulysses'' led to the discovery that the Sun's magnetic field interacts with the Solar System in a more complex fashion than previously assumed.
* Data provided by ''Ulysses'' led to the discovery that the Sun's magnetic field interacts with the Solar System in a more complex fashion than previously assumed.
* Data provided by ''Ulysses'' led to the discovery that dust coming into the Solar System from deep space was 30 times more abundant than previously expected.
* Data provided by ''Ulysses'' led to the discovery that dust coming into the Solar System from deep space was 30 times more abundant than previously expected.
* In 2007–2008 data provided by ''Ulysses'' led to the determination that the magnetic field emanating from the Sun's poles is much weaker than previously observed.
* In 2007–2008 data provided by ''Ulysses'' led to the determination that the magnetic field emanating from the Sun's poles is much weaker than previously observed.
* That the [[solar wind]] has "grown progressively weaker during the mission and is currently at its weakest since the start of the Space Age".<ref name="NASA JPL"/>
* That the [[solar wind]] has "grown progressively weaker during the mission and is currently at its weakest since the start of the Space Age".<ref name=nasa-20090630/>


==Fate==
==Fate==
Ulysses will most likely continue in heliocentric orbit around the Sun indefinitely. However, there is a chance that in one of its re-encounters with Jupiter a close fly-by with one of the Jovian moons would be enough to alter its course and so the probe would enter a [[hyperbolic trajectory]] around the Sun and [[List of artificial objects leaving the Solar System|leave the Solar System]].<ref>{{Cite news|url=https://www.reuters.com/article/us-space-solar-idINTRE5600A220090701|title = Solar orbiter Ulysses ends mission after 18 years|newspaper = Reuters|date = July 2009}}</ref>
''Ulysses'' will most likely continue in heliocentric orbit around the Sun indefinitely. However, there is a chance that in one of its re-encounters with Jupiter a close fly-by with one of the Jovian moons would be enough to alter its course and so the probe would enter a [[hyperbolic trajectory]] around the Sun and [[List of artificial objects leaving the Solar System|leave the Solar System]].<ref name=reuters1/>


== See also ==
== See also ==
{{Portal|Spaceflight}}
{{Portal|Spaceflight}}
* [[List of heliophysics missions]]
* {{annotated link|Advanced Composition Explorer}}
** [[Advanced Composition Explorer]]
* {{annotated link|List of heliophysics missions}}
** [[Parker Solar Probe]]
* {{annotated link|List of missions to the outer planets}}
** [[Solar and Heliospheric Observatory|SOHO]]
* {{annotated link|Parker Solar Probe}}
* {{annotated link|Solar and Heliospheric Observatory}}
** [[Solar Dynamics Observatory]]
** [[Solar Orbiter]]
* {{annotated link|STEREO}}
** [[STEREO]]
* {{annotated link|TRACE}}
** [[TRACE]]
* {{annotated link|Wind (spacecraft)|''WIND''}}
** [[Wind (spacecraft)|WIND]]
* {{annotated link|Solar Orbiter|''Solar Orbiter''}}
* [[List of missions to the outer planets]]
** [[Galileo project|Galileo]]


== References ==
== References ==
{{Reflist|30em}}
{{Reflist|refs=

<ref name="arstech1">{{cite web
| author1= Emily Carney
| title= A deathblow to the Death Star: The rise and fall of NASA's Shuttle-Centaur
| url= https://arstechnica.com/science/2015/10/dispatches-from-the-death-star-the-rise-and-fall-of-nasas-shuttle-centaur/
| website= Ars Technica
| date= 9 October 2015
| access-date= 22 June 2024 }}
</ref>

<ref name="esa-20080612">{{cite web
| title= Sun to set on Ulysses solar mission on 1 July
| url= https://www.esa.int/Science_Exploration/Space_Science/Sun_to_set_on_Ulysses_solar_mission_on_1_July2
| website= www.esa.int
| publisher= [[European Space Agency|ESA]]
| date= 12 June 2008
| access-date= 22 June 2024 }}
</ref>

<ref name="esa-20090630">{{cite web
| url= https://www.esa.int/Enabling_Support/Operations/Ulysses_12_extra_months_of_valuable_science
| title= Ulysses: 12 Extra Months of Valuable Science
| website= www.esa.int
| publisher= [[European Space Agency|ESA]]
| date= 30 June 2009
| access-date= 1 July 2009 }}
</ref>

<ref name="Gloeckler_2004">{{cite journal
| author1= G. Gloeckler
| author2= F. Allegrini
| author3= H. A. Elliott
| author4= D. J. McComas
| author5= N. A. Schwadron
| author6= J. Geiss
| author7= R. von Steiger
| author8= G. H. Jones
| display-authors= 4
| date= 1 April 2004
| title= Cometary Ions Trapped in a Coronal Mass Ejection
| journal= [[The Astrophysical Journal]]
| volume= 604
| issue= 2
| pages= L121–L124
| doi= 10.1086/383524
| bibcode= 2004ApJ...604L.121G
| issn= 0004-637X }}
</ref>

<ref name="nasa1">{{cite web
| title= Ulysses – NASA Science
| url= https://science.nasa.gov/mission/ulysses/
| website= science.nasa.gov
| publisher= [[NASA]]
| access-date= 1 August 2021 }}
</ref>

<ref name="nasa-20080612">{{cite web
| author1= D. C. Brown
| author2= DC Agle
| title= International Mission Studying Sun to Conclude
| url= https://www.jpl.nasa.gov/news/international-mission-studying-sun-to-conclude
| website= jpl.nasa.gov
| publisher= [[NASA]] / [[Jet Propulsion Laboratory|JPL]]
| date= 12 June 2008
| access-date= 1 August 2021 }}
</ref>

<ref name="nasa-20090630">{{cite web
| author1= DC Agle
| author2= M. Petrovich
| author3= D. C. Brown
| author4= M. Talevi
| url= https://www.jpl.nasa.gov/news/ulysses-spacecraft-ends-historic-mission-of-discovery
| title= Ulysses Spacecraft Ends Historic Mission of Discovery
| website= jpl.nasa.gov
| publisher= [[NASA]] / [[Jet Propulsion Laboratory|JPL]]
| date= 30 June 2009
| access-date= 1 July 2009 }}
</ref>

<ref name="reuters1">{{cite news
| author1= Steve Gorman
| url= https://www.reuters.com/article/us-space-solar-idINTRE5600A220090701
| title = Solar orbiter Ulysses ends mission after 18 years
| newspaper = [[Reuters]]
| date= 1 July 2009
| access-date= 26 August 2024 }}
</ref>

<ref name="ulysses.ops-1">{{cite web
| url= http://ulysses-ops.jpl.esa.int/ulsfct/opsfiles/03feb_ops.html
| title= Ulysses Mission Ops (February 2003)
| publisher= [[European Space Agency|ESA]]
| format= HTML
| archive-date= 3 July 2009
| archive-url= https://web.archive.org/web/20090703055833/http://ulysses-ops.jpl.esa.int/ulsfct/opsfiles/03feb_ops.html
| url-status= dead }}
</ref>

<ref name="ulysses.ops-2">{{cite web
| title= Ulysses Mission Ops (May 2008)
| url= http://ulysses-ops.jpl.esa.int/ulsfct/opsfiles/08may_ops.html
| publisher= [[European Space Agency|ESA]]
| format= HTML
| archive-date= 2 December 2008
| archive-url=https://web.archive.org/web/20081202042239/http://ulysses-ops.jpl.esa.int/ulsfct/opsfiles/08may_ops.html#max-512bps
| url-status= dead }}
</ref>

}}


== External links ==
== External links ==
Line 197: Line 309:
* [https://web.archive.org/web/20061101094503/http://www.mps.mpg.de/de/projekte/ulysses/ Max Planck Institute ''Ulysses'' website]
* [https://web.archive.org/web/20061101094503/http://www.mps.mpg.de/de/projekte/ulysses/ Max Planck Institute ''Ulysses'' website]
* [http://www.planetary.org/radio/show/00000303/ Interview with ''Ulysses'' Mission Operations Manager Nigel Angold on Planetary Radio] {{Webarchive|url=https://web.archive.org/web/20120220052841/http://www.planetary.org/radio/show/00000303/ |date=20 February 2012 }}
* [http://www.planetary.org/radio/show/00000303/ Interview with ''Ulysses'' Mission Operations Manager Nigel Angold on Planetary Radio] {{Webarchive|url=https://web.archive.org/web/20120220052841/http://www.planetary.org/radio/show/00000303/ |date=20 February 2012 }}
*[https://thehappykoala.github.io/Harmony-of-the-Spheres/#/scenario/Ulysses%20-%20Leaving%20the%20Ecliptic Interactive 3D visualisation of Ulysses Jupiter gravity assist and polar orbit around the Sun]
*[https://thehappykoala.github.io/Harmony-of-the-Spheres/#/scenario/Ulysses%20-%20Leaving%20the%20Ecliptic Interactive 3D visualisation of ''Ulysses'' Jupiter gravity assist and polar orbit around the Sun]


{{Sun spacecraft}}
{{Sun spacecraft}}

Revision as of 11:55, 6 September 2024

Ulysses
The Ulysses spacecraft being tested in ESTEC, Netherlands around 1985
NamesOdysseus
Mission typeHeliophysics
OperatorNASA / ESA
COSPAR ID1990-090B Edit this at Wikidata
SATCAT no.20842
WebsiteNASA Page
ESA Page
Mission duration18 years, 8 months and 24 days[1]
Spacecraft properties
ManufacturerAstrium GmbH, Friedrichshafen
(formerly Dornier Systems)
Launch mass371 kg (818 lb)[2]
Payload mass55 kg (121 lb)
Dimensions3.2 × 3.3 × 2.1 m (10.5 × 10.8 × 6.9 ft)
Power285 watts
Start of mission
Launch date6 October 1990, 11:47:16 UTC[2]
RocketSpace Shuttle Discovery
STS-41/IUS-PAM-S
Launch siteKennedy, LC-39B
ContractorNASA
End of mission
DisposalDecommissioned
Deactivated30 June 2009
Orbital parameters
Reference systemHeliocentric
Perihelion altitude1.35 AU (202 million km)
Aphelion altitude5.40 AU (808 million km)
Inclination79.11°
Period2,264.26 days (6.1992 years)
Flyby of Jupiter (gravity assist)
Closest approach8 February 1992
Distance440,439 km (273,676 mi)
Ulysses mission insignia
Ulysses mission patch

Ulysses (/jˈlɪsz/ yoo-LISS-eez, UK also /ˈjlɪsz/ YOO-liss-eez) was a robotic space probe whose primary mission was to orbit the Sun and study it at all latitudes. It was launched in 1990 and made three "fast latitude scans" of the Sun in 1994/1995, 2000/2001, and 2007/2008. In addition, the probe studied several comets. Ulysses was a joint venture of the European Space Agency (ESA) and the United States' National Aeronautics and Space Administration (NASA), under leadership of ESA with participation from Canada's National Research Council.[3] The last day for mission operations on Ulysses was 30 June 2009.[4][5]

To study the Sun at all latitudes, the probe needed to change its orbital inclination and leave the plane of the Solar System. To change the orbital inclination of a spacecraft to about 80° requires a large change in heliocentric velocity, the energy to achieve which far exceeded the capabilities of any launch vehicle. To reach the desired orbit around the Sun, the mission's planners chose a gravity assist maneuver around Jupiter, but this Jupiter encounter meant that Ulysses could not be powered by solar cells. The probe was powered instead by a General Purpose Heat Source Radioisotope Thermoelectric Generator (GPHS-RTG).[6]

The spacecraft was originally named Odysseus, because of its lengthy and indirect trajectory to study the solar poles. It was renamed Ulysses, the Latin translation of "Odysseus", at ESA's request in honor not only of Homer's mythological hero but also of Dante's character in the Inferno.[7] Ulysses was originally scheduled for launch in May 1986 aboard the Space Shuttle Challenger on STS-61-F. Due to the 28 January 1986 loss of Challenger, the launch of Ulysses was delayed until 6 October 1990 aboard Discovery (mission STS-41).

Spacecraft

Ulysses spacecraft

The spacecraft was designed by ESA and built by Dornier Systems, a German aircraft manufacturer. The body was roughly a box, approximately 3.2 m × 3.3 m × 2.1 m (10.5 ft × 10.8 ft × 6.9 ft) in size. The box mounted the 1.65 m (5 ft 5 in) dish antenna and the GPHS-RTG radioisotope thermoelectric generator (RTG) power source. The box was divided into noisy and quiet sections. The noisy section abutted the RTG; the quiet section housed the instrument electronics. Particularly "loud" components, such as the preamps for the radio dipole, were mounted outside the structure entirely, and the box acted as a Faraday cage.

Ulysses was spin-stabilised about its z-axis which roughly coincides with the axis of the dish antenna. The RTG, whip antennas, and instrument boom were placed to stabilize this axis, with the spin rate nominally at 5 rpm. Inside the body was a hydrazine fuel tank. Hydrazine monopropellant was used for course corrections inbound to Jupiter, and later used exclusively to repoint the spin axis (and thus, the antenna) at Earth. The spacecraft was controlled by eight thrusters in two blocks. Thrusters were pulsed in the time domain to perform rotation or translation. Four Sun sensors detected orientation. For fine attitude control, the S-band antenna feed was mounted slightly off-axis. This offset feed combined with the spacecraft spin introduced an apparent oscillation to a radio signal transmitted from Earth when received on board the spacecraft. The amplitude and phase of this oscillation were proportional to the orientation of the spin axis relative to the Earth direction. This method of determining the relative orientation is called conical scanning and was used by early radars for automated tracking of targets and was also very common in early infrared guided missiles.

The spacecraft used S-band for uplinked commands and downlinked telemetry, through dual redundant 5-watt transceivers. The spacecraft used X-band for science return (downlink only), using dual 20 watts TWTAs until the failure of the last remaining TWTA in January 2008. Both bands used the dish antenna with prime-focus feeds, unlike the Cassegrain feeds of most other spacecraft dishes.

Dual tape recorders, each of approximately 45-megabit capacity, stored science data between the nominal eight-hour communications sessions during the prime and extended mission phases.

The spacecraft was designed to withstand both the heat of the inner Solar System and the cold at Jupiter's distance. Extensive blanketing and electric heaters protected the probe against the cold temperatures of the outer Solar System.

Multiple computer systems (CPUs/microprocessors/Data Processing Units) are used in several of the scientific instruments, including several radiation-hardened RCA CDP1802 microprocessors. Documented 1802 usage includes dual-redundant 1802s in the COSPIN, and at least one 1802 each in the GRB, HI-SCALE, SWICS, SWOOPS and URAP instruments, with other possible microprocessors incorporated elsewhere.[8]

Total mass at launch was 371 kg (818 lb), of which 33.5 kg was hydrazine propellant used for attitude control and orbit correction.

Instruments

Ulysses instruments
Ulysses radial boom test

The twelve different Instruments came from ESA and NASA. The first design was based on two probes, one by NASA and one by ESA, but the probe of NASA was defunded and in the end the instruments of the cancelled probe were mounted on Ulysses.[9]

  • Radio/Plasma antennas: Two beryllium copper antennas were unreeled outwards from the body, perpendicular to the RTG and spin axis. Together this dipole spanned 72 meters (236.2 ft). A third antenna, of hollow beryllium copper, was deployed from the body, along the spin axis opposite the dish. It was a monopole antenna, 7.5 meters (24.6 ft) long. These measured radio waves generated by plasma releases, or the plasma itself as it passed over the spacecraft. This receiver ensemble was sensitive from DC to 1 MHz.[10]
  • Experiment Boom: A third type of boom, shorter and much more rigid, extended from the last side of the spacecraft, opposite the RTG. This was a hollow carbon-fiber tube, of 50 mm (2 in.) diameter. It can be seen in the photo as the silver rod stowed alongside the body. It carried four types of instruments: a solid-state X-ray instrument, composed of two silicon detectors, to study X-rays from solar flares and Jupiter's aurorae; the Gamma-Ray Burst experiment, consisting of two CsI scintillator crystals with photomultipliers; two different magnetometers, a helium vector magnetometer and a fluxgate magnetometer; and a two-axis magnetic search coil antenna measured AC magnetic fields.
  • Body-Mounted Instruments: Detectors for electrons, ions, neutral gas, dust, and cosmic rays were mounted on the spacecraft body around the quiet section.
  • Lastly, the radio communications link could be used to search for gravitational waves[11] (through Doppler shifts) and to probe the Sun's atmosphere through radio occultation. No gravitational waves were detected.
  • Total instrument mass was 55 kg.
  • Magnetometer (MAG): MAG measured the magnetic field in the heliosphere. Measurements of Jupiter's magnetic field were also performed. Two magnetometers performed Ulysses' magnetic field measurements, the Vector Helium Magnetometer and the Fluxgate Magnetometer.[12]
  • Solar Wind Plasma Experiment (SWOOPS): detected the solar wind at all solar distances and latitudes and in three dimensions. It measured positive ions and electrons.[13]
  • Solar Wind Ion Composition Instrument (SWICS): determined composition, temperature and speed of the atoms and ions that comprise the solar wind.[14][15]
  • Unified Radio and Plasma Wave Instrument (URAP): picked up radio waves from the Sun and electromagnetic waves generated in the solar wind close to the spacecraft.
  • Energetic Particle Instrument (EPAC) and GAS: EPAC investigated the energy, fluxes and distribution of energetic particles in the heliosphere. GAS studied the uncharged gases (helium) of interstellar origin.
  • Low-Energy Ion and Electron Experiment (HI-SCALE): investigated the energy, fluxes and distribution of energetic particles in the heliosphere.
  • Cosmic Ray and Solar Particle Instrument (COSPIN): investigated the energy, fluxes and distribution of energetic particles and galactic cosmic rays in the heliosphere.
  • Solar X-ray and Cosmic Gamma-Ray Burst Instrument (GRB): studied cosmic gamma ray bursts and X-rays from solar flares.
  • Dust Experiment (DUST): Direct measurements of interplanetary and interstellar dust grains to investigate their properties as functions of the distance from the Sun and solar latitude.

Mission

Planning

Ulysses sits atop the PAM-S and IUS combination
Illustration of Ulysses after deployment
Illustration of the International Solar Polar Mission on IUS

Until Ulysses, the Sun had only been observed from low solar latitudes. The Earth's orbit defines the ecliptic plane, which differs from the Sun's equatorial plane by only 7.25°. Even spacecraft directly orbiting the Sun do so in planes close to the ecliptic because a direct launch into a high-inclination solar orbit would require a prohibitively large launch vehicle.

Several spacecraft (Mariner 10, Pioneer 11, and Voyagers 1 and 2) had performed gravity assist maneuvers in the 1970s. Those maneuvers were to reach other planets also orbiting close to the ecliptic, so they were mostly in-plane changes. However, gravity assists are not limited to in-plane maneuvers; a suitable flyby of Jupiter could produce a significant plane change. An Out-Of-The-Ecliptic mission (OOE) was thereby proposed. See article Pioneer H.

Originally, two spacecraft were to be built by NASA and ESA, as the International Solar Polar Mission. One would be sent over Jupiter, then under the Sun. The other would fly under Jupiter, then over the Sun. This would provide simultaneous coverage. Due to cutbacks, the U.S. spacecraft was cancelled in 1981. One spacecraft was designed, and the project recast as Ulysses, due to the indirect and untried flight path. NASA would provide the Radioisotope Thermoelectric Generator (RTG) and launch services, ESA would build the spacecraft assigned to Astrium GmbH, Friedrichshafen, Germany (formerly Dornier Systems). The instruments would be split into teams from universities and research institutes in Europe and the United States. This process provided the 12 instruments on board.

The changes delayed launch from February 1983 to May 1986 when it was to be deployed by the Space Shuttle Challenger (boosted by the proposed Centaur G Prime upper stage). However, the Challenger disaster forced a two-and-a-half year stand down of the shuttle fleet, mandated the cancellation of the Centaur-G upper stage, and pushed the launch date to October 1990.[16]

Launch

Ulysses after deployment from STS-41

Ulysses was deployed into low Earth orbit from the Space Shuttle Discovery. From there, it was propelled on a trajectory to Jupiter by a combination of solid rocket motors.[17] This upper stage consisted of a two-stage Boeing IUS (Inertial Upper Stage), plus a McDonnell Douglas PAM-S (Payload Assist Module-Special). The IUS was inertially stabilised and actively guided during its burn. The PAM-S was unguided and it and Ulysses were spun up to 80 rpm for stability at the start of its burn. On burnout of the PAM-S, the motor and spacecraft stack was yo-yo de-spun (weights deployed at the end of cables) to below 8 rpm prior to separation of the spacecraft. On leaving Earth, the spacecraft became the fastest ever artificially-accelerated spacecraft, and held that title until the New Horizons probe was launched.

On its way to Jupiter, the spacecraft was in an elliptical non-Hohmann transfer orbit. At this time, Ulysses had a low orbital inclination to the ecliptic.

Jupiter swing-by

Ulysses' second orbit (1999–2004)
Animation of Ulysses's trajectory from 6 October 1990 to 29 June 2009
   Ulysses  ·   Earth ·   Jupiter  ·   C/2006 P1 ·   C/1996 B2  ·   C/1999 T1

It arrived at Jupiter on 8 February 1992 for a swing-by maneuver that increased its inclination to the ecliptic by 80.2°. The giant planet's gravity bent the spacecraft's flight path southward and away from the ecliptic plane. This put it into a final orbit around the Sun that would take it past the Sun's north and south poles. The size and shape of the orbit were adjusted to a much smaller degree so that aphelion remained at approximately 5 AU, Jupiter's distance from the Sun, and perihelion was somewhat greater than 1 AU, the Earth's distance from the Sun. The orbital period is approximately six years.

Polar regions of the Sun

Between 1994 and 1995 it explored both the southern and northern polar regions of the Sun, respectively.

Comet C/1996 B2 (Hyakutake)

On 1 May 1996, the spacecraft unexpectedly crossed the ion tail of Comet Hyakutake (C/1996 B2), revealing the tail to be at least 3.8 AU in length.[18][19]

Comet C/1999 T1 (McNaught–Hartley)

An encounter with a comet tail happened again in 2004[20] when Ulysses flew through the ion tailings of C/1999 T1 (McNaught-Hartley). A coronal mass ejection carried the cometary material to Ulysses.[19][21]

Second Jupiter encounter

Ulysses approached aphelion in 2003/2004 and made further distant observations of Jupiter.[22]

Comet C/2006 P1 (McNaught)

In 2007, Ulysses passed through the tail of comet C/2006 P1 (McNaught). The results were surprisingly different from its pass through Hyakutake's tail, with the measured solar wind velocity dropping from approximately 700 kilometers per second (1,566,000 mph) to less than 400 kilometers per second (895,000 mph).[23]

Extended mission

Ulysses Radioisotope thermoelectric generator

ESA's Science Program Committee approved the fourth extension of the Ulysses mission to March 2004 [24] thereby allowing it to operate over the Sun's poles for the third time in 2007 and 2008. After it became clear that the power output from the spacecraft's RTG would be insufficient to operate science instruments and keep the attitude control fuel, hydrazine, from freezing, instrument power sharing was initiated. Up until then, the most important instruments had been kept online constantly, whilst others were deactivated. When the probe neared the Sun, its power-hungry heaters were turned off and all instruments were turned on.[25]

On 22 February 2008, 17 years and 4 months after the launch of the spacecraft, ESA and NASA announced that the mission operations for Ulysses would likely cease within a few months.[26][27] On 12 April 2008, NASA announced that the end date will be 1 July 2008.[28]

The spacecraft operated successfully for over four times its design life. A component within the last remaining working chain of X-band downlink subsystem failed on 15 January 2008. The other chain in the X-band subsystem had previously failed in 2003.[29]

Downlink to Earth resumed on S-band, but the beamwidth of the high gain antenna in the S-band was not as narrow as in the X–band, so that the received downlink signal was much weaker, hence reducing the achievable data rate. As the spacecraft traveled on its outbound trajectory to the orbit of Jupiter, the downlink signal would have eventually fallen below the receiving capability of even the largest antennas (70 meters - 229.7 feet - in diameter) of the Deep Space Network.

Even before the downlink signal was lost due to distance, the hydrazine attitude control fuel on board the spacecraft was considered likely to freeze, as the radioisotope thermal generators (RTGs) failed to generate enough power for the heaters to overcome radiative heat loss into space. Once the hydrazine froze, the spacecraft would no longer be able to maneuver to keep its high gain antenna pointing towards Earth, and the downlink signal would then be lost in a matter of days. The failure of the X-band communications subsystem hastened this, because the coldest part of the fuel pipework was routed over the X-band traveling-wave tube amplifiers, because they generated enough heat during operation to keep the propellant plumbing warm.

The previously announced mission end date of 1 July 2008, came and went but mission operations continued albeit in a reduced capacity. The availability of science data gathering was limited to only when Ulysses was in contact with a ground station due to the deteriorating S-band downlink margin no longer being able to support simultaneous real-time data and tape recorder playback.[30] When the spacecraft was out of contact with a ground station, the S-band transmitter was switched off and the power was diverted to the internal heaters to add to the warming of the hydrazine. On 30 June 2009, ground controllers sent commands to switch to the low gain antennas. This stopped communications with the spacecraft, in combination with previous commands to shut down its transmitter entirely.[4][31]

Results

STS-41 launches from Kennedy Space Center, 6 October 1990.

During cruise phases, Ulysses provided unique data. As the only spacecraft out of the ecliptic with a gamma-ray instrument, Ulysses was an important part of the InterPlanetary Network (IPN). The IPN detects gamma ray bursts (GRBs); since gamma rays cannot be focused with mirrors, it was very difficult to locate GRBs with enough accuracy to study them further. Instead, several spacecraft can locate the burst through multilateration. Each spacecraft has a gamma-ray detector, with readouts noted in tiny fractions of a second. By comparing the arrival times of gamma showers with the separations of the spacecraft, a location can be determined, for follow-up with other telescopes. Because gamma rays travel at the speed of light, wide separations are needed. Typically, a determination came from comparing: one of several spacecraft orbiting the Earth, an inner-Solar-System probe (to Mars, Venus, or an asteroid), and Ulysses. When Ulysses crossed the ecliptic twice per orbit, many GRB determinations lost accuracy.

Additional discoveries:[32][2]

  • Data provided by Ulysses led to the discovery that the Sun's magnetic field interacts with the Solar System in a more complex fashion than previously assumed.
  • Data provided by Ulysses led to the discovery that dust coming into the Solar System from deep space was 30 times more abundant than previously expected.
  • In 2007–2008 data provided by Ulysses led to the determination that the magnetic field emanating from the Sun's poles is much weaker than previously observed.
  • That the solar wind has "grown progressively weaker during the mission and is currently at its weakest since the start of the Space Age".[31]

Fate

Ulysses will most likely continue in heliocentric orbit around the Sun indefinitely. However, there is a chance that in one of its re-encounters with Jupiter a close fly-by with one of the Jovian moons would be enough to alter its course and so the probe would enter a hyperbolic trajectory around the Sun and leave the Solar System.[33]

See also

References

  1. ^ "Ulysses". NASA's Solar System Exploration website. Retrieved 25 September 2023.
  2. ^ a b c "Ulysses – NASA Science". science.nasa.gov. NASA. Retrieved 1 August 2021.
  3. ^ "Welcome to the HIA Ulysses Project". Herzberg Institute of Astrophysics. Archived from the original on 17 August 2011. The Herzberg Institute of Astrophysics (HIA) of the National Research Council of Canada provided instrumentation and test equipment for the COsmic ray and Solar Particle INvestigation (COSPIN) on the Ulysses spacecraft. The COSPIN instrument consists of five sensors which measure energetic nucleons and electrons over a wide range of energies. This was the first participation by Canada in a deep-space interplanetary mission.
  4. ^ a b "Ulysses: 12 Extra Months of Valuable Science". www.esa.int. ESA. 30 June 2009. Retrieved 1 July 2009.
  5. ^ "The odyssey concludes..." Archived from the original on 24 February 2012.
  6. ^ https://rps.nasa.gov/missions/13/ulysses/ [bare URL]
  7. ^ "Inferno of Ulysses' urge to explore an uninhabited world behind the Sun. In Jane's Spaceflight Directory 1988, ISBN 0-7106-0860-8
  8. ^ Ulysses NASA Documentation Archive Archived March 17, 2013, at the Wayback Machine Public Domain This article incorporates text from this source, which is in the public domain.
  9. ^ "Ulysses factsheet". esa.int. Retrieved 7 May 2021.
  10. ^ Unified Radio and Plasma Wave Investigation, JPL Archived January 17, 2009, at the Wayback Machine
  11. ^ The Gravity Wave Experiment, Astronomy and Astrophysics Archived December 19, 2008, at the Wayback Machine
  12. ^ Balogh, A.; Beek, T. J.; Forsyth, R. J.; Hedgecock, P. C.; Marquedant, R. J.; Smith, E. J.; Southwood, D. J.; Tsurutani, B. T. (20 August 1991). "The magnetic field investigation on the ULYSSES mission - Instrumentation and preliminary scientific results". Astronomy & Astrophysics Supplement Series. 91 (2): 221–236. Bibcode:1992A&AS...92..221B.
  13. ^ Goldstein, Bruce. SWOOPS/Electron – User Notes Archived September 27, 2006, at the Wayback Machine, Jet Propulsion Laboratory
  14. ^ Geiss, J; Gloeckler, G; von Steiger, R; Balsiger, H; Fisk, L.; Galvin, A.; Ipavich, F.; Livi, S; McKenzie, J.; Ogilvie, K.; et, al. (19 May 1995). "The southern high-speed stream: results from the SWICS instrument on Ulysses". Science. 268 (5213): 1033–1036. Bibcode:1995Sci...268.1033G. doi:10.1126/science.7754380. ISSN 0036-8075. PMID 7754380.
  15. ^ von Steiger, R.; Geiss, J.; Gloeckler, G.; Galvin, A. B. (1 April 1995). "Kinetic properties of heavy ions in the solar wind from SWICS/Ulysses". Space Science Reviews. 72 (1): 71–76. Bibcode:1995SSRv...72...71V. doi:10.1007/BF00768756. ISSN 1572-9672. S2CID 189797680.
  16. ^ Emily Carney (9 October 2015). "A deathblow to the Death Star: The rise and fall of NASA's Shuttle-Centaur". Ars Technica. Retrieved 22 June 2024.
  17. ^ "Sun to set on Ulysses solar mission on 1 July". www.esa.int. ESA. 12 June 2008. Retrieved 22 June 2024.
  18. ^ Jones G. H.; Balogh A.; Horbury T. S. (2000). "Identification of comet Hyakutake's extremely long ion tail from magnetic field signatures". Nature. 404 (6778): 574–576. Bibcode:2000Natur.404..574J. doi:10.1038/35007011. PMID 10766233. S2CID 4418311.
  19. ^ a b "Ulysses Catches Another Comet by the Tail". sci.esa.int. Retrieved 22 June 2024.
  20. ^ Poletto, Giannina; Suess, Steve T. (5 June 2013). The Sun and the Heliosphere as an Integrated System. Springer. ISBN 9781402028311.
  21. ^ G. Gloeckler; F. Allegrini; H. A. Elliott; D. J. McComas; et al. (1 April 2004). "Cometary Ions Trapped in a Coronal Mass Ejection". The Astrophysical Journal. 604 (2): L121–L124. Bibcode:2004ApJ...604L.121G. doi:10.1086/383524. ISSN 0004-637X.
  22. ^ Ulysses - Science - Jupiter Distant Encounter Selected References Archived September 23, 2008, at the Wayback Machine Public Domain This article incorporates text from this source, which is in the public domain.
  23. ^ Neugebauer, Gloeckle (1 October 2007). "Encounter of the Ulysses Spacecraft with the Ion Tail of Comet McNaught". The Astrophysical Journal. 667 (2): 1262–1266. Bibcode:2007ApJ...667.1262N. doi:10.1086/521019.
  24. ^ ESA Science & Technology: Ulysses Mission Extended
  25. ^ "Ulysses scores a hat-trick". www.esa.int. Retrieved 22 June 2024.
  26. ^ "Ulysses mission coming to a natural end". European Space Agency. 22 February 2008. Retrieved 23 February 2008.
  27. ^ "International Solar Mission to End Following Stellar Performance". NASA. 22 February 2008. Retrieved 23 February 2008. Public Domain This article incorporates text from this source, which is in the public domain.
  28. ^ "RIP: Ulysses solar probe coming to end soon - Yahoo! News". Archived from the original on 17 June 2008. Retrieved 15 January 2017.
  29. ^ "Ulysses Mission Ops (February 2003)". ESA. Archived from the original (HTML) on 3 July 2009.
  30. ^ "Ulysses Mission Ops (May 2008)". ESA. Archived from the original (HTML) on 2 December 2008.
  31. ^ a b DC Agle; M. Petrovich; D. C. Brown; M. Talevi (30 June 2009). "Ulysses Spacecraft Ends Historic Mission of Discovery". jpl.nasa.gov. NASA / JPL. Retrieved 1 July 2009.
  32. ^ D. C. Brown; DC Agle (12 June 2008). "International Mission Studying Sun to Conclude". jpl.nasa.gov. NASA / JPL. Retrieved 1 August 2021.
  33. ^ Steve Gorman (1 July 2009). "Solar orbiter Ulysses ends mission after 18 years". Reuters. Retrieved 26 August 2024.