Mars Surveyor '98 program
|
|
The Mars Surveyor '98 program was comprised of two spacecraft launched separately, the Mars Climate Orbiter (formerly the Mars Surveyor '98 Orbiter) and the Mars Polar Lander (formerly the Mars Surveyor '98 Lander), on board Mars Polar Lander spacecraft were two surface-penetrator probes (Deep Space 2) The two missions were to study the Martian weather, climate, and water and carbon dioxide budget, in order to understand the reservoirs, behavior, and atmospheric role of volatiles and to search for evidence of long-term and episodic climate changes.
Both spacecraft were launched during the 1998 Mars orbit insertion launch window. Both spacecraft were lost, including the penetrator probes.
The orbiter was lost due to a miscalculation in trajectory. The miscalculation was caused by an unintended and undetected mismatch between metric and English units of measurement. The use of metric units as well as the data formats to employ were specified in a navigation software interface specification (SIS) published by JPL in 1996. Despite this, the flight operations team at Lockheed Martin provided impulse data in English units of pound-force seconds rather than newton seconds. These values were incorrect by a factor of 4.45 (1 lbf = 4.45 N). The mix-up caused erroneous course corrections that resulting in the orbiter descending too low in Mars atmosphere. The vehicle either burned up or bounced off into space.
The most likely cause of the Lander’s failure, investigators decided, was that a spurious sensor signal associated with the craft’s legs falsely indicated that the craft had touched down when in fact it was some 40 meters above the surface. When the landing lags unfolded they made a bouncing motion that accidentally set of the landing sensors, thus caused the descent engines to shut down prematurely and the Lander to free-fall out of the Martian sky. Another possible reasons for failure was inadequate preheating of catalysis beds for the pulsing rocket thrusters. Hydrazine fuel decomposes on the beds to make hot gases that throttle out the rocket nozzles; cold catalysis beds caused misfiring and instability in crash review tests.
The Mars Surveyor 1998 program spacecraft development cost US$193.1 million. Launch costs were estimated at US$91.7 million and mission operations at US$42.8 million. The Mars Climate Orbiter was part of NASA's 10-year Mars Surveyor Program, which feature launches every 26 months when the Earth and Mars are favorably aligned.