No. 46 - Preparation and Entry into Passive Cruise Mode
01 August 2005 21:13Report for Period 15-29 July 2005
The reporting period was dedicated to the preparation and entry into Passive Cruise Mode. This was the first time that this mode is entered operationally during the mission. The spacecraft will remain in this low activity, low bitrate mode over the next two months.
In the first week of the reporting period some outstanding maintenance activities were carried out on the on-board software parameter tables, including fine tuning of FDIR thresholds and addition of new on-board monitoring items (19 July), and the finalisation of thermal control thresholds and upload of the new TCT table in SGM EEPROM (20 July). On 21 July a confidence test was carried out to verify the TC bitrate of 250 bps, needed for the incoming passive cruise arc.
On 25 July the spacecraft was slewed to the Near Sun Hibernation Mode entry attitude and on the following day, 26 July, the Passive Cruise Mode was entered, including transition to NSHM and configuration of all subsystems for the new spacecraft mode. On 27 July, after a verification of the nominal status of the spacecraft, a test with the New Norcia ground station was carried out to verify the capability to lock on the downlink signal with narrow Phase Lock Loop bandwidth. Finally on 28th of July the spacecraft was configured to low TM and TC bitrates and TM modulation switched off at the end of the pass. This completed the activities related to entry in Passive Cruise Mode.
No payload operations were carried out in the reporting period. SREM was kept active in the background for the entire period, and configured for a lower data collection rate to cope with the reduced visibility periods and bitrates available during the incoming passive cruise period.
A total of 7 New Norcia passes of a maximum duration of about 9 hours commanding were taken over the reporting period.
The mark of 100 million km distance from Earth was passed in the evening of Sunday 24 July.
At the end of the reporting period (DOY 210) Rosetta was at 107.3 million Km from the Earth. The one-way signal travel time was 5 min 57 sec.