Mission description
Lander computer
Rover characteristics
Rover power
Power electronics
Mission lifetime
Technical Information
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Fact sheet Mission description Lander computer Rover characteristics Rover power Power electronics Mission lifetime Technical Information |
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Flight System Characteristics
Launch Mass 890 Kg (Includes Propellant)
Entry Mass 570 Kg
Lander Mass 360 KG
Computation R6000 Computer With VME Bus,
22 Millions Of Instructions Per Second (MIPS),
128 Mbyte mass memory
Telemetry And Command Surface Operations Telemetry Rate Via High Gain Antenna,
Total Mass 16 KG
Mobile Mass 11.5 Kg including deployment mechanism
Instrument Lander-Mounted Rover Equipment Mass:4.5 Kg including ultra-high
frequency (UHF) modem and support structure.
Autonomous Navigation On board, using laser striping for obstacle detection
Mobility System Six-wheel, rocker bogie suspension
Command And Telemetry UHF link with lander
Payload aft and fore cameras, APXS, APXS deployment mechanism
Power 0.25-M Solar panels, peak power 16 W-hours: primary battery, 50 W-hours
Thermal Control
Three radioisotope header units (RHUs)
Computer Characteristics 80C85, 0.1 MIPS; 0.5 Mbyte RAM mass storage;
0.5 Kg, 1.5 W
Surface Ops Time 10 A.M. to 2 P.M. each martian day (sol HR)
As other Mars Landers and Rovers, Pathfinder was tested in the MarsYard
Of course, all of Sojourner's equipment, including her computers, lasers, motors, and radio modem require power. Sojourner generated most of her power using a lightweight solar array. The array is easily visible as a flat panel mounted on the top of the Rover. The panel is actually made up of an "array" of over two hundred photovoltaic solar cells. Each cell is about the size and width of a double-edge razor blade. The cells are very light, thin, and fragile.
By electrically connecting these cells together in strings, the solar array provided Sojourner with around 16 watts of power at noon on Mars. That's equivalent to the power used by a oven light, yet it allowed the power-efficient Rover to perform almost all her nominal mission activities.
During the times when there was either too little or no sunlight for the solar array, Sojourner could use batteries to power the Rover hardware. Battery power was used cautiously since the batteries store only a limited amount of energy and once depleted, could not be recharged. They were primarily used for night time experiments and early morning operations on Mars, but also provided power for periodic Rover communications ("health checks") during the seven month cruise from Earth.
The three batteries are normally out of sight inside the Rover's gold-colored electronics box mounted under the solar panel. Each battery looks something like a black flashlight tube (without end caps) and each tube has three D-size cells inside it. The tubes are strapped together around the Rover's suspension axle which runs through the middle of the electronics box.
Should either the batteries or the solar array have failed, the Rover could have completed its primary mission using the other power source.
The power generated by the solar array and batteries was conditioned and distributed using a complex arrangement of Power Electronics. The electronics were fully integrated with the navigation and computer electronics to save money, space, and mass, and yet still provided more than ten different voltages to the various Rover hardware. Most of the power electronic components that was used are commercially available.
The mission however did not last that long because the battery on the lander failed late September 1997, because of the battery failure the temperature of the lander dropped way below the normal operating temperatures, this caused the lander to stop functioning. It is likely that the rover was still functioning long past the failure of the lander and may still be driving around the lander, trying to reestablish communications, the rover was programmed to do so if it has not been "speaking" with the lander for 9 days. The lander had operated nearly three times its design lifetime of 30 days, and the Sojourner rover operated 12 times its design lifetime of seven days.
Power 16.5 W on Mars at noon
45 W 1 sun/AMO(Earth)
Operating Voltage 14-18 volts
Weight 0.340 kg
Size 0.22 m2
Survival Temp -140 to +110 C
Battery Technical Information
Chemistry Lithium-Thionyl Chloride
Size D-Size
Weight 118 grams
Capacity +25C 12 amp-hrs
-20C 8 amp-hrs
Number of batteries 3
Cells Per Battery 3 cells in series
Size 40 mm dia, 186 mm length
Weight 1.24 kg
Operating Voltage 8 - 11 volts
Power Electronics Technical Information
User Voltages
Main bus 8 to 18 volts
Secondary +/-12v,9v,+/-7.5v,5v,+/-5v,3.3v
| Module | Mass (Kg) | propellant mass | Propulsion | Instrument payload | Electric power |
|---|---|---|---|---|---|
| Lander | 360Kg | ? Kg | Eight 4.4-N thrusters Total delta-v 130 m/s (during cruice) | ? | 3 Solar panels |
| Rover | 11,5 Kg | -- | -- | 4,5 Kg | 3 batterys 50W hours ,solar panel 16W hours |