Rosetta
European Space Agency
No. 64 - Fourth Passive Payload Checkout
September 7, 2006
Report for the period 18 August - 01 September 2006
The reporting period covers two weeks of active cruise. Operations
performed during this period included the fourth passive payload
checkout and a thermal characterisation.
The thermal characterisation was performed on the night between the 31
August and the 01September to confirm that the spacecraft can remain
indefinitely in an attitude corresponding to a solar aspect angle of
110
degrees at a Sun distance of 1 AU or more. The temperature of the
bottom-mounted spacecraft units was closely monitored in near
real-time.
All units almost reached steady state well within their defined
temperature limits.
The third passive payload checkout (PC2) was performed outside
visibility in the period 25 - 29 August. In addition the RSI passive
checkout, which requires ground contact, took place on 22 August over
New Norcia. All instruments (except GIADA and ROSINA) were activated
and
checked out in sequence. The data generated during the checkout were
dumped over thefollowing two ground station passes and are under
analysis by the instrument teams.
SREM was kept continuously active in the background for the entire
reporting period.
A total of 4 New Norcia passes of 8.7 hours commanding in average were
taken during the reporting period. TM/TC links with the OCC have been
established for all NNO passes. In addition, two tracking passes of 4
hours have been taken with DSN.
NNO Date DOY Main Activity
Pass
906 22.08.06 234 RSI Checkout - Uplink Passive Checkout Timeline
907 23.08.06 235 Monitor pass - WOL
914 30.08.06 242 Dump Passive Checkout Data - WOL
915 31.08.06 243 Dump Passive Checkout Date - Thermal
Characterisation (SAA 110?? at 1 AU)
At the end of the reporting period (DOY 244) Rosetta was at 288.0
million km from Earth (1.93 AU; one-way signal travel time was 15
minutes 26 seconds). The distance to the Sun was 156.3 million km (1.04
AU).
Spacecraft Status
Thermal
The thermal behaviour of the spacecraft is nominal and stable. It
remains configured for Active Near Sun cruise (ACM1 since DOY
207/2006).
A thermal characterisation was performed on DOY243/244 to confirm that
the spacecraft can sustain thermally an attitude corresponding to a
solar aspect angle (angle between the +Z spacecraft axis and the Sun
direction) of 110 degrees at Sun distances of 1 AU or more. Until now,
the maximum solar aspect angle that had been characterised successfully
for indefinite operations was 95??.
The spacecraft remained in the characterisation’s attitude for 13
hours.
Two emergency slews which had been loaded on the Mission Timeline in
case some spacecraft temperatures would reach their upper limits during
the test were deleted in real-time during the pass.
The monitored units included the front and bottom thrusters, the RCS
lines and the NTO tank temperatures. All units showed a clear
temperature increase, but remained within the defined limits and almost
reached steady state during the test. The maximum temperature was
reached by thrusters 4 and 5 (bottom front attitude thrusters), which
reported 52.5 ??C during the test. This is well within the hard
limit of
60 ??C defined for these thrusters. The temperature of bottom
thrusters
10 and 11 reached about 45 ??C, leading to an expected spurious
triggering of the on-board Thermal Control Application Program. The
diagram below illustrates the evolution of the temperature of thrusters
4, 5, 10 and 11 during the test.
Evolution of Thrusters 4, 5, 10 and 11 Temperatures during Thermal
Characterisation
The instruments temperatures as reported by the TRPs decreased during
the test. The test attitude was such that the HGA shaded partially the
+X face of the spacecraft (angle between the +X spacecraft axis and the
Earth direction of -40 ??C). As a result, the temperature of the
two
MGAs, as well as of thrusters 2 and 7 (upper front attitude thrusters)
decreased significantly during the test.
Payload
SREM remains active in the background for radiation monitoring with
accumulation parameters configured for active cruise.
On DOY 234, the passive checkout 3 for RSI was successfully executed
over New Norcia, according to the defined timeline. All TTC subsystem
and ground station operations were executed nominally.
The payload passive checkout was executed between DOY 237 and DOY 241.
All instruments were activated individually in sequence via MTL
commands, with the exception of ROSINA and GIADA. All activities took
place as usual outside coverage. All commands were successfully
executed
and all data downlinked over the two New Norcia passes on DOY 234/235
and 235/236. Many out-of-limit alarms and anomaly events were generated
by the instruments, most of which were expected or have already been
declared as normal by the relevant instrument teams. The data analysis
is on-going and a final report of the checkout activities will be
produced separately.
Ground Stations
A total of 4 New Norcia passes were taken over the reporting period.
The
station performed nominally during the reporting period. On DOY 236,
the
station support to Rosetta was shortened by 7.25 hours due to a safe
mode support request by Mars Express.
Future Milestones
The Mars Swingby Phase formally started on the 28 July 2006. The actual
swingby will take place on the 25 February 2007 and will be followed by
a Deep Space Manoeuver in April 2007.
Upcoming short-term operations include another thermal characterisation
and a Deep Space Manoeuvre in September and the first payload Active
Checkout (PC4) in November/December.