 Artist's conception of theMars Climate Orbiter | |
| Names | Mars Surveyor '98Orbiter |
|---|---|
| Mission type | Mars orbiter |
| Operator | NASA/JPL |
| COSPAR ID | 1998-073A |
| SATCATno. | 25571 |
| Website | science.nasa.gov |
| Mission duration | 286 days Mission failure |
| Spacecraft properties | |
| Manufacturer | Lockheed Martin |
| Launch mass | 638 kg (1,407 lb)[1] |
| Power | 500 watts |
| Start of mission | |
| Launch date | December 11, 1998, 18:45:51 (1998-12-11UTC18:45:51Z) UTC |
| Rocket | Delta II 7425 D-264 |
| Launch site | CCAFSSLC-17A |
| Contractor | Boeing |
| End of mission | |
| Disposal | Destroyed |
| Last contact | 23 September 1999 09:06:00 (1999-09-23UTC09:07Z) UTC Unintentionally deorbited |
| Orbital parameters | |
| Reference system | Areocentric |
| Epoch | Planned |
 Mars Surveyor 98 mission logo | |
TheMars Climate Orbiter (formerly theMars Surveyor '98 Orbiter) was arobotic space probe launched byNASA on December 11, 1998, to study theMartian climate,Martian atmosphere, andsurface changes and to act as the communications relay in theMars Surveyor '98 program forMars Polar Lander. However, on September 23, 1999, communication with the spacecraft was permanently lost as it went intoorbital insertion. The spacecraft encountered Mars on a trajectory that brought it too close to the planet, and it was destroyed in the atmosphere.[2] An investigation attributed the failure to a measurement mismatch between two measurement systems:SI units (metric) by NASA andUS customary units by spacecraft builderLockheed Martin.[3]
After the loss ofMars Observer and the onset of the rising costs associated with the futureInternational Space Station,NASA began seeking less expensive, smaller probes for scientific interplanetary missions. In 1994, the Panel on Small Spacecraft Technology was established to set guidelines for future miniature spacecraft. The panel determined that the new line of miniature spacecraft should be under 1,000 kg (2,200 lb) with highly focused instrumentation.[4] In 1995, a new Mars Surveyor program began as a set of missions designed with limited objectives, low costs, and frequent launches. The first mission in the new program wasMars Global Surveyor, launched in 1996 to map Mars and provide geologic data using instruments intended forMars Observer.[5] Following Mars Global Surveyor,Mars Climate Orbiter carried two instruments, one originally intended for Mars Observer, to study the climate and weather of Mars.
The primary science objectives of the mission included:[6]
TheMars Climate Orbiter bus measured 2.1 m (6 ft 11 in) tall, 1.6 m (5 ft 3 in) wide and 2.0 m (6 ft 7 in) deep. The internal structure was largely constructed with graphite composite/aluminum honeycomb supports, a design found in many commercialairplanes. With the exception of the scientific instruments, battery and main engine, the spacecraft included dual redundancy on the most important systems.[6][7] The spacecraft weighed 638 kg (1,407 lb).[1]
The spacecraft wasthree-axis stabilized and included eighthydrazinemonopropellant thrusters: four 22 N (4.9 lbf) thrusters to perform trajectory corrections and four 0.9 N (3.2 ozf) thrusters tocontrol attitude. Orientation of the spacecraft was determined by astar tracker, twoSun sensors and twoinertial measurement units. Orientation was controlled by firing the thrusters or using threereaction wheels. To perform the Mars orbital insertion maneuver, the spacecraft also included aLEROS 1B main engine rocket,[8] providing 640 N (140 lbf) of thrust by burninghydrazine fuel withnitrogen tetroxide (NTO) oxidizer.[6][7]
The spacecraft included a 1.3 m (4 ft 3 in)high-gain antenna to transceive data with theDeep Space Network over thex band. The radio transponder designed for theCassini–Huygens mission was used as a cost-saving measure. It also included a two-wayUHF radio frequency system to relay communications withMars Polar Lander upon an expected landing on December 3, 1999.[6][7][9]
The space probe was powered with athree-panel solar array, providing an average of 500 W at Mars. Deployed, the solar array measured 5.5 m (18 ft 1 in) in length. Power was stored in 12-cell, 16-amp-hournickel-hydrogen batteries. The batteries were intended to be recharged when the solar array received sunlight and power the spacecraft as it passed into the shadow of Mars. When entering into orbit around Mars, the solar array was to be utilized in theaerobraking maneuver, to slow the spacecraft until a circular orbit was achieved. The design was largely adapted from guidelines from the Small Spacecraft Technology Initiative outlined in the book,Technology for Small Spacecraft.[6][7][4]
In an effort to simplify previous implementations of computers on spacecraft,Mars Climate Orbiter featured a single computer using an IBMRAD6000 processor implementing thePOWER1ISA, capable of 5, 10 or 20 MHz operation. Data storage was to be maintained on 128MB ofrandom-access memory (RAM) and 18 MB offlash memory. The flash memory was intended to be used for highly important data, including triplicate copies of the flight system software.[6]
The Pressure Modulated Infrared Radiometer (PMIRR) 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.[10] Its principal investigator was Daniel McCleese at JPL/CALTECH. Similar objectives were later achieved withMars Climate Sounder on boardMars Reconnaissance Orbiter. Its objectives:[11]
TheMars Color Imager (MARCI) is a two-camera (medium-angle/wide-angle) imaging system designed to obtain pictures of the Martian surface and atmosphere. Under proper conditions, resolutions up to 1 km (3,300 ft) are possible.[12][13] The principal investigator on this project was Michael Malin atMalin Space Science Systems and the project was reincorporated onMars Reconnaissance Orbiter.
Its objectives:[12]
| Date | Time (UTC) | Event |
|---|---|---|
| Dec 11 1998 | 18:45:51 | Spacecraft launched |
| Sep 23 1999 | 08:41:00 | Insertion begins. Orbiter stows solar array. |
| 08:50:00 | Orbiter turns to correct orientation to begin main engine burn. | |
| 08:56:00 | Orbiter fires pyrotechnic devices which open valves to begin pressurizing the fuel and oxidizer tanks. | |
| 09:00:46 | Main engine burn starts; expected to fire for 16 minutes 23 seconds. | |
| 09:04:52 | Communication with spacecraft lost | |
| 09:06:00 | Orbiter expected to enter Marsoccultation, out of radio contact with Earth.[n 1] | |
| 09:27:00 | Expected to exit Mars occultation.[n 1] | |
| Sep 25 1999 | Mission declared a loss. Reason for loss known. No further attempts to contact. |
TheMars Climate Orbiter probe was launched on December 11, 1998, at 18:45:51 UTC by NASA fromSpace Launch Complex 17A at theCape Canaveral Air Station in Florida, aboard aDelta II 7425 launch vehicle. The complete burn sequence lasted 42 minutes bringing the spacecraft into aHohmann transfer orbit, sending the probe into a 9.5-month, 669 million km (416 million mi) trajectory.[6][9] At launch,Mars Climate Orbiter weighed 638 kg (1,407 lb) including propellant.[1]
Mars Climate Orbiter began the planned orbital insertion maneuver on September 23, 1999, at 09:00:46 UTC.Mars Climate Orbiter went out of radio contact when the spacecraft passed behind Mars at 09:04:52 UTC, 49 seconds earlier than expected, and communication was never reestablished. Due to complications arising fromhuman error, the spacecraft encountered Mars at a lower-than-anticipated altitude and it was either destroyed in the atmosphere or re-entered heliocentric space after leaving Mars's atmosphere.[2]Mars Reconnaissance Orbiter has since completed most of the intended objectives for this mission.
The problem here was not the error; it was the failure of NASA's systems engineering, and the checks and balances in our processes, to detect the error. That's why we lost the spacecraft.
On November 10, 1999, theMars Climate Orbiter Mishap Investigation Board released a Phase I report, detailing the suspected issues encountered with the loss of the spacecraft.
Previously, on September 8, 1999, Trajectory Correction Maneuver-4 (TCM-4) was computed, and was then executed on September 15, 1999. It was intended to place the spacecraft at an optimal position for an orbital insertion maneuver that would bring the spacecraft around Mars at an altitude of 226 km (140 mi) on September 23, 1999.
However, during the week between TCM-4 and the orbital insertion maneuver, the navigation team reported that it appeared the insertion altitude could be much lower than planned, at about 150–170 km (93–106 mi). Twenty-four hours prior to orbital insertion, calculations placed the orbiter at an altitude of 110 km (68 mi). 80 km (50 mi) was the minimum altitude thatMars Climate Orbiter was thought to be capable of surviving during this maneuver.
During insertion, the orbiter was intended to skim through Mars's upper atmosphere, graduallyaerobraking for weeks, but post-failure calculations showed that the spacecraft's trajectory would have taken it within 57 km (35 mi) of the surface. At this altitude, the spacecraft would likely have skipped violently off the denser-than-expected atmosphere,[citation needed] and it was either destroyed in the atmosphere, or re-entered heliocentric space.[2]
The primary cause of this discrepancy was that one piece of ground software supplied byLockheed Martin produced results in aUnited States customary unit, contrary to its Software Interface Specification (SIS), while a second system, supplied by NASA, expected those results to be inSI units, in accordance with the SIS. Specifically, software that calculated the totalimpulse produced by thruster firings produced results inpound-force seconds. The trajectory calculation software then used these results – expected to be innewton-seconds (incorrect by a factor of 4.45)[2] – to update the predicted position of the spacecraft.[2]
Still, NASA does not place the responsibility on Lockheed for the mission loss; instead, various officials at NASA have stated that NASA itself was at fault for failing to make the appropriate checks and tests that would have caught the discrepancy.[14]
The discrepancy between calculated and measured position, resulting in the discrepancy between desired and actual orbit insertion altitude, had been noticed earlier by at least two navigators, whose concerns were dismissed because they "did not follow the rules about filling out [the] form to document their concerns". A meeting of trajectory software engineers, trajectory software operators (navigators), propulsion engineers, and managers was convened to consider the possibility of executing Trajectory Correction Maneuver-5, which was in the schedule. Attendees of the meeting recall an agreement to conduct TCM-5, but it was ultimately not done.[14]
The loss of the Mars Climate Orbiter took place two and a half months before the loss of theMars Polar Lander. Inadequate funding and poor management have been cited as underlying causes of the failures. According to Thomas Young, chairman of the Mars Program Independent Assessment Team, the Mars Surveyor '98 program "was under funded by at least 30%."[15]
According to NASA, the cost of the mission was $327.6 million ($586.41 million in 2024)[16] total for the orbiter and lander, comprising $193.1 million ($345.65 million in 2024)[16] for spacecraft development, $91.7 million ($164.14 million in 2024)[16] for launching it, and $42.8 million ($76.61 million in 2024)[16] for mission operations.[7]
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