SMART-1: Second Push-Broom Operations Phase

http://sci.esa.int/science-e/www/obj...objectid=39291

Second Push-Broom Operations Phase
SMART-1
European Space Agency
23 May 2006

Report for period 17 April to 14 may 2006

The completion of the thermal analysis being done as part of the
preparation for the SMART-1 Moon impact gave the Flight Control Team a
surprise. The expected increase of temperatures during May due to the
Sun/Earth/Moon alignment was going to be higher than six months ago.

This especially affects the solar arrays at perilune when SMART-1
passes
the subsolar point with the Sun on one side and the illumination by
light reflected of the full Moon on the other, causing temperatures to
rise above 105 ??C. This would be close to the qualification limit
of the
solar arrays of 110 ??C.

After several considerations including the trend analysis of the real
time telemetry, it was decided not to take any risk and implement a
35??
offset in the solar array orientation, enough to keep it within a
reasonable range of temperatures. This was implemented on 9 May 2006
and
proved to be successful, lowering the maximum reached temperature to
around 85 ??C instead of the 96 ??C prior to the implementation
of the
offset.

Other SMART-1 operations have been nominal during this period which saw
the start of the second push-broom observations phase.

Moon impact preparation:

* Flight Dynamics strategy is completed
* The Swedish Space Corporation Analysis is completed
* The Thermal analysis and simulations are completed
* The new procedures development, testing and validation are
completed
* The SMART-1 Principal Investigator, Bernard Foing is finalizing
the coordination of the SMART-1 Moon impact and observation
campaign

The SMART-1 Ground Operations Automation System (GOAS) will be used
operationally in the second half of May, which is a first for an ESA
mission.

Future Activities

The future activities are focused on the following:

* Procedures development to raise the orbit by 90 km using the
attitude thrusters in June/July
* Finalise documentation and release of the end of mission and Moon
impact analysis
* Tone ranging test on SMART-1 with Chinese CLTC Kashi station and
with ISRO
* Start using the SMART-1 Ground Operations Automation System (S1
GOAS)
* Preparation of papers for Spaceops and IAA in Valencia

Note: The second ranging test with the Chinese station Kashi is now
confirmed for week 22.

Spacecraft Status

AOCS
The AOC subsystem has done well in the reporting period. The solar
array
off-pointing and the push-broom activities did not affect the overall
performance of the AOCS.

Electric Propulsion, Power and Thermal

Electric Propulsion
The Electric Propulsion has been off during the reporting period.

Power
The reporting period saw the start of an eclipse season. The evolution
of the eclipse duration can be seen in the plot.

Eclipse duration in hh:mm:ss (total for Umbra and Penumbra)

During the reporting period the maximum eclipse occured on 14 may and
lasted just over one hour:

Time (UT) Event
22:02:53 SMART-1 enters Moon Penumbra
22:03:23 SMART-1 enters Moon Umbra
23:02:45 SMART-1 leaves Moon Umbra
23:03:26 SMART-1 leaves Moon Penumbra

The performance of the Power Subsystem was very good. As part of the
routine analysis during the eclipse, a check of the battery cell
capacity was done, showing that there is no degradation of the cells
and
that the performance is as expected, when compared with previous
eclipses.

Thermal
The Thermal Subsystem has performed very well during the reporting
period.

Orbital Information

SMART-1 OD432 Close to Apolune 2363
Epoch (UTC) 2006/05/15 09:50:25.0

Elements WRT Moon and its equator of date

Pericentre Distance (km) 2133.593201
Apocentre Distance (km) 4703.495591
Semi Major Axis (km) 3418.544396
Eccentricity 0.375877
Inclination (??) 90.852895
Ascending Node (??) 239.345651
Argument of Pericentre (??) 232.698778
True Anomaly (??) 180.000000
Osculating Orbital Period (h) 4.982153

The changes in four parameters since apolune 2329 a

* semi-major axis -0.3 km
* perilune height -36.3 km
* apolune height +35.7 km
* orbital period -0.0 min