Editing Mars Observer (section)

=== Spacecraft design ===

The ''Mars Observer'' spacecraft had a mass of {{convert|1018|kg|lb}}. Its [[Satellite bus|bus]] measured 1.1 meters tall, 2.2 meters wide, and 1.6 meters deep. The spacecraft was based on previous satellite designs, originally intended and developed to orbit Earth. The RCA AS-4000 Ku-band satellite design was used extensively for the spacecraft bus, propulsion, thermal protection, and solar array. RCA [[Television Infrared Observation Satellite|TIROS]] and [[Defense Meteorological Satellite Program|DMSP Block 50-2]] satellite designs were also utilized in the implementing the Attitude and Articulation Control System (AACS), command and data handling subsystem, and power subsystem, into ''Mars Observer''. Other elements such as the bipropellant components and high-gain antenna were designed specifically for the mission.{{r|MOSafetyReview|NSSDC|MOLaunchPressKit}}

==== Attitude control and propulsion ====
:The spacecraft was [[3-axis stabilized spacecraft|three-axis stabilized]] with four [[reaction wheel]]s and twenty-four [[reaction engine|thrusters]] with 1,346 kilograms of propellant. The propulsion system was a  high thrust, monomethyl hydrazine/nitrogen tetroxide bipropellant system for larger maneuvers and a lower thrust [[hydrazine]] [[monopropellant rocket|monopropellant]] system for minor orbital corrections during the mission. Of the bipropellant thrusters, four located on the aft, provide 490 [[Newton (unit)|newtons]] of thrust for course corrections, control of the spacecraft during the Mars orbital insertion maneuver and large orbit corrections during the mission; another four, located on along the sides of the spacecraft, provide 22&nbsp;newtons for controlling roll maneuvers. Of the hydrazine thrusters, eight provide 4.5&nbsp;newtons to control orbit trim maneuvers; another eight provide 0.9&nbsp;newtons for offsetting, or "desaturating", the reaction wheels. To determine the orientation of the spacecraft, a [[Astrionics#Earth Horizon Sensor|horizon sensor]], a 6-slit star scanner, and five [[Sun sensor]]s were included.{{r|MOSafetyReview|MOLaunchPressKit}}

==== Communications ====
[[File:Mars Observer - HGA diagram.png|thumb|150px|alt=Proposed antenna configuration for combine X/Ka operation (1986)|Proposed X/Ka band antenna (1986)]]
:For telecommunications, the spacecraft included a two-axis [[gimbal]]ed 1.5 meter, parabolic [[high-gain antenna]], mounted to a 6 meter boom to communicate with the [[Deep Space Network]] across the [[X-band]] using two GFP NASA X-band transponders (NXTs) and two GFP command detector units (CDUs). An assembly of six low-gain antennas, and a single medium-gain antenna were also included, to be used during the cruise phase while the high-gain antenna remained stowed, and for contingency measures should communications through the high-gain antenna become restricted. When broadcasting to the Deep Space Network, a maximum of 10.66 kilobytes/second could be achieved while the spacecraft could receive commands at a maximum bandwidth of 62.5 bytes per second.{{r|Astronautix|MOSafetyReview|NSSDC|MOLaunchPressKit}}

:There was also a research payload, the Mars Observer Ka-Band Link Experiment (KABLE), designed to measure performance for possible future missions at Ka-band. It was very low power, intended only for measurements and not operational use.<ref>{{cite web |url=https://tda.jpl.nasa.gov/progress_report/42-88/88S.PDF |title=A K-a band (32 GHz) Beacon Link Experiment (KABLE) With Mars Observer |year=1986}} Proposal.</ref><ref>{{cite web |url=https://core.ac.uk/download/pdf/42785642.pdf |title=The Mars Observer Ka-Band Link Experiment |year=1994}} Final report.</ref>

==== Power ====
:Power was supplied to the spacecraft through a six-panel [[photovoltaic array|solar array]], measuring 7.0&nbsp;meters wide and 3.7&nbsp;meters tall, and would provide an average of 1,147&nbsp;watts when in orbit. To power the spacecraft while [[occultation|occluded]] from the Sun, two 42&nbsp;A·h [[Nickel-cadmium battery|nickel-cadmium batteries]] were included; the batteries would recharge as the solar array received sunlight.{{r|Astronautix|MOSafetyReview|NSSDC|MOLaunchPressKit}}

==== Computer ====
:The computing system on the spacecraft was a retooling of the system used on the TIROS and DMSP satellites. The semiautonomous system was able to store up to 2,000 commands in the included 64 kilobytes of [[random-access memory]], and execute them at a maximum rate of 12.5 commands/second; commands could also provide sufficient autonomous operation of the spacecraft for up to sixty days. To record data, redundant digital tape recorders (DTR) were included and each capable of storing up to 187.5 megabytes, for later playback to the Deep Space Network.<ref name=MOSafetyReview/>

==== Scientific instruments ====
{|
| colspan="2" style="background: #e5e5e5"  | [[Mars Orbiter Camera|Mars Observer Camera]] ('''MOC''')
|-
| [[File:Mars Observer - MOC2 cb.jpg|150px]] <br />'''-'''[[:File:Mars Observer - MOC Diagram.png|see diagram]]
|
{| style="float: right;" class="collapsible collapsed" width="300px"
|-
! style="background: #f2f2f2" | Objectives<ref name=MOObjectives/>
|-
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*Obtain global synoptic views of the Martian atmosphere and surface to study meteorological, climatological, and related surface changes.
*Monitor surface and atmosphere features at moderate resolution for changes on time scales of hours, days, weeks, months and years.
*Systematically examine local areas at extremely high spatial resolution in order to quantify surface/atmosphere interactions and geological processes.
|}
Consists of narrow-angle and wide-angle telescopic cameras to study the meteorology/climatology and geoscience of Mars.<ref name=NSSDCMOC/>
*{{small|'''Principal investigator:''' Michael Malin / Arizona State University ([http://www.msss.com/all_projects/mars-observer-moc.php website])}}
*{{small|reincorporated on '''[[Mars Global Surveyor]]'''}}
|-
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|-
| colspan="2" style="background: #e5e5e5"  | [[Mars Orbiter Laser Altimeter|Mars Observer Laser Altimeter]] ('''MOLA''')
|-
| [[File:Mars Observer - MOLAincolor.jpg|150px]] <br />'''-'''[[:File:Mars Observer - MOLA Diagram.png|see diagram]]
|
{| style="float: right;" class="collapsible collapsed" width="300px"
! style="background: #f2f2f2" | Objectives<ref name=MOObjectives/>
|-
|
* Provide topographic height measurements with a vertical resolution better than 0.5% of the elevation change within the footprint.
* Provide RMS slope information over the footprint.
* Provide surface brightness temperatures at 13.6&nbsp;GHz with a precision of better than 2.5K.
* Provide well sampled radar return wave forms for precise range corrections and the characterization of surface properties.
|}
A [[Laser ranging#Physics and astronomy|laser altimeter]] used to define the [[topography]] of [[Mars]].<ref name=NSSDCMOLA/>
*{{small|'''Principal investigator:''' David Smith / NASA Goddard Space Flight Center}}
*{{small|reincorporated on '''[[Mars Global Surveyor]]'''}}
|-
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|-
| colspan="2" style="background: #e5e5e5"  | [[Thermal Emission Spectrometer]] ('''TES''')
|-
| [[File:Mars Observer - MGSTESpic sm.gif|150px]] <br />'''-'''[[:File:Mars Observer - TES Diagram.png|see diagram]]
|
{| style="float: right;" class="collapsible collapsed" width="300px"
! style="background: #f2f2f2" | Objectives<ref name=MOObjectives/>
|-
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* Determine and map the composition of surface minerals, rocks and ice.
* Study the composition, particle size, and spatial and tempora distribution of atmospheric dust.
* Locate water-ice and carbon dioxide condensate clouds and determine their temperature, height and condensate abundance.
* Study the growth, retreat and total energy balance of the polar cap deposits.
* Measure the thermophysical properties of the Martian surface (thermal inertia, albedo) used to derive surface particle size and rock abundance.
* Determine atmospheric temperature, pressure, water vapor, and ozone profiles, and seasonal pressure variations.
|}
Uses three sensors (Michelson interferometer, solar reflectance sensor, broadband radiance sensor) to measure thermal infrared emissions to map the mineral content of surface rocks, frosts and the composition of clouds.<ref name=NSSDCTES/>
*{{small|'''Principal investigator:''' Philip Christensen / Arizona State University}}
*{{small|reincorporated on '''[[Mars Global Surveyor]]'''}}
|-
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|-
| colspan="2" style="background: #e5e5e5"  | Pressure Modulator Infrared Radiometer ('''PMIRR''')
|-
| [[File:Mars Observer - PMIRR Diagram.png|150px]]
|
{| style="float: right;" class="collapsible collapsed" width="300px"
! style="background: #f2f2f2" | Objectives<ref name=MOObjectives/>
|-
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* Map the three-dimensional and time-varying thermal structure of the atmosphere from the surface to 80&nbsp;km altitude.
* Map the atmospheric dust loading and its global, vertical and temporal variation.
* Map the seasonal and spatial variation of the vertical distribution of atmospheric water vapor to an altitude of at least 35&nbsp;km.
* Distinguish between atmospheric condensates and map their spatial and temporal variation.
* Map the seasonal and spatial variability of atmospheric pressure.
* Monitor the polar radiation balance.
|}
Uses narrow-band radiometric channels and two pressure modulation cells to measure atmospheric and surface emissions in the thermal infrared and a visible channel to measure dust particles and condensates in the atmosphere and on the surface at varying longitudes and seasons.<ref name=NSSDCPMIRR/>
*{{small|'''Principal investigator:''' Daniel McCleese / JPL}}
*{{small|reincorporated on '''[[Mars Climate Orbiter]]''' and then further developed and flown on '''[[Mars Reconnaissance Orbiter]]'''}}
|-
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|-
| colspan="2" style="background: #e5e5e5"  | Gamma Ray Spectrometer ('''GRS''')
|-
| [[File:Mars Observer - GRS.png|150px]] <br />'''-'''[[:File:Mars Observer - GRS Diagram.png|see diagram]]
|
{| style="float: right;" class="collapsible collapsed" width="300px"
! style="background: #f2f2f2" | Objectives<ref name=MOObjectives/>
|-
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* Determine the elemental composition of the surface of Mars with a spatial resolution of a few hundred kilometers through measurements of incident gamma-rays and albedo neutrons ([[Hydrogen|H]], [[Oxygen|0]], [[Magnesium|Mg]], [[Aluminum|Al]], [[Silicon|Si]], [[Sulfur|S]], [[Chlorine|Cl]], [[Potassium|K]], [[Iron|Fe]], [[Thorium|Th]], [[Uranium|U]]).
* Determine hydrogen depth dependence in the top tens of centimeters.
* Determine the atmospheric column density.
* Determine the arrival time and spectra of gamma-ray bursts.
|}
Records the spectrum of [[gamma rays]] and [[neutron]]s emitted by the radioactive decay of [[Chemical element|elements]] contained in the Martian surface.<ref name=NSSDCGRS/>
*{{small|'''Principal investigator:''' William Boynton / University of Arizona / NASA Goddard Space Flight Center ([http://heasarc.gsfc.nasa.gov/docs/heasarc/missions/marsobs.html#instrumentation HEASARC website])}}
*{{small|reincorporated on '''[[2001 Mars Odyssey]]'''}}
|-
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|-
| colspan="2" style="background: #e5e5e5"  | [[Magnetometer]] and Electron Reflectometer ('''MAG'''/'''ER''')
|-
| [[File:Mars Observer - ER.gif|150px]]
|
{| style="float: right;" class="collapsible collapsed" width="300px"
! style="background: #f2f2f2" | Objectives<ref name=MOObjectives/>
|-
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* Establish the nature of the magnetic field of Mars.
* Develop models for its representation, which take into account the internal sources of magnetism and the effects of the interaction with the solar wind.
* Map the Martian crustal remanlint field using the fluxgate sensors and extend these in-situ measurements with the remote capability of the electron-reflectometer sensor.
* Characterize the solar wind/Mars plasma interaction.
* Remotely sense the Martian ionosphere.
|}
Uses the components of the on-board telecommunications system and the stations of the [[Deep Space Network]] to collect data on the nature of the [[magnetic field]] and interactions the field may have with [[solar wind]].<ref name=NSSDCMAGER/>
*{{small|'''Principal investigator:''' Mario Acuna / NASA Goddard Space Flight Center}}
*{{small|reincorporated on '''[[Mars Global Surveyor]]'''}}
|-
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|-
| colspan="2" style="background: #e5e5e5"  | Radio Science experiment ('''RS''')
|-
| [[File:Mars Observer - RS Diagram.png|150px]]
|
{| style="float: right;" class="collapsible collapsed" width="300px"
! style="background: #f2f2f2" | Objectives<ref name=MOObjectives/>
|-
| '''Atmosphere'''
* Determine profiles of refractive index, number density, temperature, and pressure at the natural experimental resolution (approx. 200&nbsp;m) for the lowest few scale heights at high latitudes in both hemispheres on a daily basis.
* Monitor both short term and seasonal variation in atmospheric stratification.
* Characterize the thermal response of the atmosphere to dust loading.
* Explore the thermal structure of the boundary layer at high vertical resolution (approx. 10&nbsp;m).
* Determine the height and peak plasma density of the daytime ionosphere.
* Characterize the small scale structure of the atmosphere and ionosphere.
|-
| '''Gravity'''
* Develop a global, high-resolution model for the gravitational field.
* Determine both local and broad scale density structure and stress state of the Martian crust and upper mantle.
* Detect and measure temporal changes in low degree harmonics of the gravitational field.
|}
Collects data on the [[gravity field]] and the [[Martian atmosphere|Martian atmospheric structure]] with a special emphasis on temporal changes near the polar regions.<ref name=NSSDCRS/>
*{{small|'''Principal investigator:''' G. Tyler / Stanford University}}
*{{small|reincorporated on '''[[Mars Global Surveyor]]'''}}
|-
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|-
| colspan="2" style="background: #e5e5e5"  | Mars Balloon Relay ('''MBR''')
|-
| <!--[[File:|150px]]-->
|
Planned as augmentation to return data from the penetrators and surface stations of the Russian Mars '94 mission and from penetrators, surface stations, a rover, and a balloon from the [[Mars 96|Mars '96]] mission.<ref name=NSSDCMBR/>
*{{small|'''Principal investigator:''' Jacques Blamont / Centre National de la Recherche Scientifique}}
*{{small|reincorporated on '''[[Mars Global Surveyor]]'''}}
|-
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|-
|}<ref name=Astronautix/><ref name=NSSDC/>

{{Gallery|align=center|title=Images of the spacecraft |width=175 |File:Mars Observer - spacecraft diagram -rev2.png|alt1=Labeled diagram of Mars Observer |{{small|Labeled diagram of ''Mars Observer''.}}
|File:Mars Observer preparations.jpg|alt2=Mars Observer in the Payload Hazardous Servicing Facility |{{small|''Mars Observer'' in the Payload Hazardous Servicing Facility.}}
|File:Mars Observer - marsobs 2.png|alt3=Technician assembling the Mars Observer space probe |{{small|Technician assembling the ''Mars Observer'' space probe.}}
|File:Mars - Observermarsobs 3.png|alt4=Mars Observer in the clean room |{{small|''Mars Observer'' in the clean room.}}
}}