NASA's Stardust probe on track for Earth flyby
NASA/JPL STATUS REPORT
Posted: January 6, 2001
Known as Trajectory Correction Maneuver No. 5, the event provided the final targeting for Stardust's Earth flyby. The craft is within 4,000,000 km from the Earth and closing rapidly.
The probe will make its closest approach to Earth at 1115 GMT (6:15 a.m. EST) on January 15 in a pre-planned gravity assist to sling-shot the probe on its continued trek to collect samples of Comet Wild 2 and return to our home planet over the next several years.
There is a small possibility that Stardust may be visible from Earth after flyby using sophisticated telescopes with CCD detectors.
Five Navigation Camera images were taken on Friday to assess camera performance after the second heating sequence where both the CCD and mirror motor heaters were turned on for about one month. These images were to be played back later Friday. The spacecraft will then be left alone until after Earth flyby.
During the holiday period there were numerous Deep Space Network (DSN) tracking passes with Stardust. NASA reports all subsystems onboard the spacecraft are performing normally.
In preparation for the Earth Gravity Assist, the Command Loss Timer was changed to three days from its usual value of nine days. The CLT is an onboard countdown clock based on the last successful command received by the spacecraft. When the CLT reaches zero or when there is no communication from Earth for nine days -- the safe mode executive assumes there is a problem somewhere in the spacecraft's uplink path and requests safe mode.
The SME will then autonomously swap components in the uplink path, pausing in between swaps, until a command is received. Since Stardust is rapidly approaching EGA, the command loss time was reduced to three days to allow a faster recovery in the unlikely failure of an uplink component. This strategy will allow the spacecraft team to respond to a failure and ensure that critical commands are successfully sent to the spacecraft in a timely manner.
Also, a timer in the SME was changed to ensure that if a safe mode entry occurs, the spacecraft will remain pointed at the Sun and not attempt to communicate with the Earth. If the spacecraft enters safe mode just prior to the closest approach, the batteries would reach their low state of charge limit (50 percent) because the Earth and Sun are 180 degrees apart. If the spacecraft enters safe mode after closest approach, the SME will command the spacecraft to a power-friendly communications attitude. This change will ensure the spacecraft remains in a safe attitude, pointed at the Sun, until the spacecraft team commands it to "phone home".