TIM FURNISS / LONDON
Predicted high winds add to agency's woes by reducing landing options to dull sites
NASA is unlikely to launch a Mars sample return mission until 2016 as it wrestles with technological challenges and the prospect of a $2 billion price tag for the flight.
The agency is already having problems with other flights, including the twin Mars Exploration Rover missions to be launched next year, it has been revealed by NASA's Jet Propulsion Laboratory.
The launch of a sample return mission was originally thought to have been possible in 2005. The double loss of the Mars Climate Orbiter and Mars Polar Lander in 1999 was a major blow to NASA's technical reputation. The next mission by two Mars Athena Exploration Rovers, planned for Delta II launches in May and June, is under threat. That $800 million mission is already $100 million over budget.
Several potential landing sites have been eliminated because of new predictions of high Martian winds, which will cause problems with the airbag balloon landing system. This has been redesigned as a result. A stabilising transverse impulse rocket system has been added to the main solid propellant retro motors, which fire before the balloon system is deployed. Accelerometer-based sensors were designed to control the exact timing of the firing otherwise stabilisation problems could occur.
NASA is now designing a second complementary sensor, called the descent imager motion estimation subsystem, to ensure the craft is at the correct angle at the moment of motor firing.
The predicted high winds have cut NASA's landing options to scientifically dull locations at Elysium and Terra Meridiani, instead of the potentially exciting Athabasca Valley and Gusev Crater (Flight International, 10-16 September).
The landing sites will be selected in January and a decision made on whether one or two Athenas will fly or whether both will be delayed. The 170kg (375lb) twin Athena Rovers are to spend three months roaming the Martian surface.
Equipped with cameras, infrared spectrometers and grinding wheels, the Athenas will confirm previous orbiters' observations about chemical activity on the planet's surface.
Source: Flight International
