No. 10 - First Earth Pointing of Payload
03 May 2004 08:36Report for week 23 to 30 April 2004
Payload commissioning activities continued in the reporting period. For the first time the spacecraft was rotated such that the payload could point towards the Earth. This gave MIRO and VIRTIS the opportunity to take calibration measurements using the Earth as a target.
Towards the end of the foreseen Earth pointing period an unplanned slew was executed to move the Sun into the +Z hemisphere as the temperature of the -Z thrusters was reaching its highest allowed limits due to Sun illumination. This manoeuvre resulted in cancelling the ALICE PAT test planned for the following pass.
The second slot of OSIRIS commissioning took the rest of the reporting period. All planned activities were executed successfully, except for the Earth-Moon imaging which had to be postponed as a precautionary measure after the high thruster temperatures observed during the MIRO Earth pointing period. This however did not affect the achievement of the OSIRIS commissioning objectives.
On the subsystem side no special activity was performed. Close monitoring of the thermal environment continues, and the experience with the Earth pointing attitude has resulted in a further restriction on the range of allowed attitudes. The Sun is now allowed in a range from -4 to +50 degrees from the +X axis in the X/Z plan, at least until after perihelion is reached on 25 May.
The table below shows a chronology of the main activities in the reporting period:
At the end of the last New Norcia pass in the reporting period (DOY 121, 02:30) Rosetta was at 23.5 million km from the Earth. The one-way signal travel time was 1 minute and 18 seconds.