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Activating Rosetta
Activating Rosetta
8 Mar 2004
(Source: European Space Agency)

Activating Rosetta
European Space Agency
March 8, 2004


The spacecraft and ground segment continue to operate well. All activities planned for the initial, critical phase after launch have been successfully completed ahead of schedule. In the early morning of 5 March the Mission Control Team at ESOC has moved from the Main Control Room to the Rosetta Dedicated Control Room to commence the spacecraft and payload commissioning.

This early relocation of the team, just 3 days after launch, is a record at ESOC and it is seen as remarkable, considering the complexity of the Rosetta spacecraft. The 5-day launch delay, from 26 February to 2 March, has been largely recovered and the early commissioning activities are now scheduled to within 1 or 2 days of the original plan. The New Norcia ground station in Australia (35 m antenna) will support the daily operations, while the support from the ESA Kourou and NASA Deep Space Network Madrid and Goldstone ground stations has been released with the termination of the critical phase. By midday on 8 March Rosetta is already 2 million km from the Earth. The signal round-trip light-time is almost 14 seconds.

Ground Stations

Location Latitude Longitude Type Size
French Guiana 05.25? N 52.80? W Beam Wave Guide 15 m

New Norcia
Australia 31.03? S 116.11? E Beam Wave Guide 35 m

DSS 24
Goldstone, USA 36.69? N 116.87? W Beam Wave Guide 34 m

DSS 54
Madrid, Spain 41.15? N 04.25? W Beam Wave Guide 34 m

Spacecraft Activities

Initial activation of S-band transmission, using the 2.2 m large dish antenna, commenced at 23:16 on 3 March. Successful commissioning of the S-band up and downlinks on the low and high gain antennas took place throughout the night. Following on from this, configuration of the X-band, also using the high gain antenna, took place with a downlink signal received at both the Kourou and Madrid ground stations at 13:07 UT.

Termination of the S-band uplink occurred at 13:20 and X-band uplink established at 13:35. The X-band uplink was then terminated at 14:30 and uplink communications were re-established via the High Gain Antenna at S-band. By 7 March, tests of the X-band communications had been completed. These activities successfully demonstrated the nominal performance of the major communication systems, which will be critical for the mission. Due to the rapidly increasing distance between the spacecraft and the Earth, the possible data rate using the low gain antenna is already limited to 7.8 bits per second and this link will soon vanish. Using the High Gain Antenna the maximum data rate of 22 kbits per second is sustainable.

The attitude control system has undergone several characterization tests, such as gyroscope calibrations and determination of the friction in the reaction wheel system. This included, for the first time, switching on all four reaction wheels simultaneously. Substantial disturbance torques acted on the spacecraft during its first few days in orbit. Over the following days these torques gradually decreased to nominal levels. The phenomenon, attributed to the outgassing of the spacecraft, diminishes with time because the spacecraft is in the high vacuum of space.

Full configuration of the 25 Gbit solid-state mass memory took place on 4 March in order to support routine operations: creating data stores for all instruments and storing redundant files of application software. Activation of all memory modules for the mission is now complete.

Commissioning of the power subsystem took place at the end of the Madrid pass on 4 March. All checks were successful and the power subsystem behaved as expected.

The drive mechanisms of the solar array are being exercised during the early days of the flight in order to keep the solar cells perpendicular to the Sun as the spacecraft rotates. The azimuth and elevation drives, enabling the High Gain Antenna to track the Earth, have been extensively characterized. These mechanical functions are critical to the mission and they are working nominally.

Overview of Activities

Note all times are in Universal Time (UT)

LOS = Loss of Signal
AOS = Acquisition of Signal
EOT = End of Transmission

3 March 2004

Bit rate changed to 52428.8 sps
Stop Uplink DSS54
Start Uplink DSS24
LOS Kourou
AOS New Norcia
Ranging stopped at DSS24
Stop Uplink DSS24
Start Uplink New Norcia
Ranging started from New Norcia
Ranging stopped at New Norcia
Stop Uplink New Norcia
Start Uplink New Norcia with reduced power before HGA activation (100 W)
HGA antenna on Transponder#1 activated. New Norcia and DSS24 have an increased input level of 32 dB

4 March 2004

Telecommunication link out
Carrier Down New Norcia
Start S-Band commissioning procedure
Switch HGA to LGA Rear
TC bitrate change to 1000 bits per second (bps)
AOS Kourou
LOS New Norcia
TC bitrate change to 250 bps on Transponder 2
TC bitrate change to 1000 bps on Transponder 1
TC bitrate change to 250 bps on Transponder 1
TC bitrate change to 7.8125 bps on Transponder 1
TC bitrate change to 2000 bps on Transponder 2
Change over to the on board Ultra Stable Oscillator
Kourou configured for X-band
X-band AOS in Kourou and DSS54
X-Band Telemetry processed from Kourou
X-Band Carrier up from Kourou
Several re-sweeps were conducted at different uplink levels (300W, 12W, 6W) in order to check the onboard AGC readings
First X-Band Command sent from Kourou
TMm Symbol rate change to 5461 sps
Switch HGA to LGA Rear
TC bitrate change to 7.8125 bits per second
LOS Kourou
AOS New Norcia
Carrier down New Norcia
Carrier up New Norcia with reduced power (100 W) after HGA Earth pointing and activation

5 March 2004

Downlink switched off Transponder 1 on LGA
Downlink switched on Transponder 2 on HGA
Transmitter 2 on-board switched on: HGA radiating in S-Band
TLM symbol rate change to 52428.88 sps. Ranging Modulation index change to 0.2 rad
Switch over from Transponder 1 to Transponder 2
Transponder switch: downlink drop Transponder 1
Transponder switch: downlink back on Transponder 2
LOS New Norcia
End of Launch and Early Orbit Phase

Planned Instrument Activities
08 Mar
First payload commissioning

11 Mar
Payload commissioning, including antenna deployment

12 Mar
Payload commissioning

12-17 Mar
Payload commissioning

17-21 Mar
Payload commissioning

Planned Spacecraft Activities

09 Mar
Change attitude to +X axis Sun pointing, test of the star trackers in the new attitude and Sun sensor alignment calibration

10 Mar
Solar array flexible modes calibration

18 Mar
RPC boom deployment

Orbit Trajectory

At 12:00 on 8 March 2004 Rosetta was 1.988 million km from Earth. This placed it more than one million km outside its sphere of influence. Orbital elements are, therefore, quoted with respect to the Sun as Earth centric information is not so relevant at such a distance. The signal round-trip time was 13.26 seconds.

EPOCH (UTC) 2004/03/08 11:58:55.8 UTC

Heliocentric state and elements (reference plane is Earth mean equator of J2000.0)

Position (km)
X -143442749.489284
Y 27368977.567599
Z 12005574.989980

Velocity (kms-1)
Xdot -3.027967
Ydot -27.696812
Zdot -11.774408

Semi Major Axis
km 148022446.315397
AU 0.9895
Eccentricity 0.105414
Inclination (?) 23.044997
Ascending Node (?) 0.340809
Argument of Pericentre (?) 258.457557
True Anomaly (?) 269.460347

Pericentre Distance
km 132418878.617842
AU 0.8852
Apocentre Distance
km 163626014.012952
AU 1.0938
Osc. Orbit Period
Hours 8628.055233
Days 359.5

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Last Updated: 9 Mar 2004