Operational history

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(Note: Adapted from Planck Collaboration 2011, A&A 536, A1)

The major operational phases and milestones are:

1. Launch and transfer to orbit: (provide date, and summary overview)

Planck was launched from the Centre Spatial Guyanais in Kourou (French Guyana) on 14 May 2009 at its nominal lift-off time of 13:12 UT, on an Ariane 5 ECA rocket of Arianespace2. ESA’s Herschel observatory was launched on the same rocket. At 13:37:55 UT, Herschel was released from the rocket at an altitude of 1200 km; Planck followed suit at 13:40:25UT. The separation attitudes of both satellites were within 0.1 deg of prediction. The Ariane rocket placed Planck with excellent accuracy (semimajor axis within 1.6% of prediction), on a trajectory towards the second Lagrangian point of the Earth-Sun system (L2). After release from the rocket, three large manoeuvres were carried out to place Planck in its intended final orbit. The first (14.35 ms−1), intended to correct for errors in the rocket injection, was executed on 15 May at 20:01:05 UT, with a slight overperformance of 0.9% and an error in direction of 1.3 deg (a touch-up manoeuvre was carried out on 16 May at 07:17:36 UT). The second and major (mid-course) manoeuvre (153.6ms−1) took place between 5 and 7 June, and a touch-up (11.8 ms−1) was executed on 17 June. The third and final manoeuvre (58.8ms−1), to inject Planck into its final orbit, was executed between 2 and 3 July. The total fuel consumption of these manoeuvres, which were carried out using Planck’s coarse (20N) thrusters, was 205 kg. Once in its final orbit, very small manoeuvres are required at approximately monthly intervals (1 ms−1 per year) to keep Planck from drifting away from its intended path around L2. The attitude manoeuvres required to follow the scanning strategy require about 2.6 ms−1 per year. Overall, the excellent performance of launch and orbit manoeuvres will lead to a large amount (∼160 kg, or ∼40% of initial tank loading) of fuel remaining on board at end of mission operations.

Planck started cooling down radiatively shortly after launch. Heaters were activated to hold the focal plane at 250 K, which was reached around 5 h after launch. The valve opening the exhaust piping of the dilution cooler was activated at 03:30 UT, and the 4He-JT cooler compressors were turned on at low stroke at 05:20 UT. After these essential operations were completed, on the second day after launch, the focal plane temperature was allowed to descend to 170 K for out-gassing and decontamination of the telescope and focal plane.

2. Calibration and Performance Verification: (provide date, and summary overview)

The first period of operations focussed on commissioning activities, i.e., functional check-out procedures of all sub-systems and instruments of the Planck spacecraft in preparation for running science operations related to calibration and performance verification of the payload. Planning for commissioning operations was driven by the telescope decontamination period of 2 weeks and the subsequent cryogenic cool-down of the payload and instruments. The overall duration of the cool-down was approximately 2 months, including the decontamination period. The sequence of commissioning activities covered the following areas:

– on-board commanding and data management;

– attitude measurement and control;

– manoeuvreing ability and orbit control;

– telemetry and telecommand;

– power control;

– thermal control;

– payload basic functionality, including:

– the LFI;

– the HFI;

– the cryogenic chain;

– the Standard Radiation Environment Monitor;

– the Fibre-Optic Gyro unit (FOG), a piggy-back experiment which is not used as part of the attitude control system.

The commissioning activities were executed very smoothly and all sub-systems were found to be in good health.

3. Nominal Mission: (provide date, and summary overview)

4. Extended Mission: (provide date, and summary overview)

5. LFI-only phase: (provide date, and summary overview)

6. End-of-life: (provide a vague estimation)

Provide a description of the product Planck Operational State History.

European Space Agency

(Planck) Low Frequency Instrument

(Planck) High Frequency Instrument

Fiber Optic Gyroscope