|status reports||27-March-2019 03:56:27|
No. 18 - Payload Commissioning
13 February 2004
The spacecraft is now in its 216th orbit, in good status and with all functions performing nominally. The electric propulsion engine was switched off on 30 January 2004 for a period of three weeks to allow instrument commissioning activities to take place.
In addition to these first technical results, the first images were important for the project as a whole with the Moon being the final destination of SMART-1.
For the following week, the Moon was not visible so the AMIE camera tried to image star fields. Its target, on 23 January, was the naked-eye open cluster the Pleiades, found in the constellation of Taurus.
During long exposures of up to 60 seconds the thermal noise limits the visibility of faint stars. The experiment provided scientists with an understanding of the thermal behaviour of the camera while taking long exposures. This should enable controllers to place a better fix on the operational constraints of the camera when imaging stars.
On 29 January, as reported in the previous status report, the camera reacquired the Moon and took images using all of its filters. As well as providing images the test also allowed mission controllers to demonstrate the excellent attitude control of the spacecraft.
On 13 February, KATE transmitted some signals in Ka band to the DSS13 in the first part of the test.
EPDP & SPEDE
Part of EPDP is a solar cell, which monitors the degradation of the solar output power due to mass deposition. The functioning of this cell needs calibration at different Sun incidence angles. On 9 February, to test different incidence angles, the spacecraft turned through a series of complex rotations.
The results show that the solar cell reacts as expected. Determination of the extent of degradation, however, requires a significant number of such experiments.
The two booms of the SPEDE instrument have been working well since the launch. The booms measure an integrated current coming from a number of different sources. One component is the photoelectron current created by both the boom and the spacecraft as a reaction to incident solar photons. By rotating the boom towards the Sun the contribution of the photoelectron current from the boom becomes nil and the boom only measures the photoelectron current from the spacecraft. A more accurate calibration of earlier data is possible once this contribution is calculated.
Unfortunately, this calibration attempt was halted. Due to the required complex spacecraft rotation, the behaviour of the spacecraft in a limit position (angle between the Sun and the solar panels at the limit of the constraints) led to an overheating of the star trackers. This produced a Safe Mode transition before the end of the calibration.
Planned Instrument Activities
11 - 17 February 2004
18 February 2004 onwards
Planned Spacecraft Activities
The ESOC specialists periodically compute the osculating orbital elements. These elements define the so-called "osculating orbit" which would be travelled by the spacecraft if at that instant all perturbations, including EP thrust, would cease. Therefore, it is an image of the situation at that epoch. In reality, the path travelled by the spacecraft is a continuous spiral leading from one orbit to another. The most recent osculating elements are as follows:
Displayed in the plot are the osculating orbits at launch (GTO) and at different times throughout the mission. The last two orbits are virtually identical as the only perturbations in the orbit are natural ones as the electric propulsion is dormant.
Bernard H. Foing
Last Update: 25 August 2006For further information please contact: SciTech.email@example.com
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