status reports 20-July-2019 15:23:38

No. 23 - Successful Orbit Insertion

19 April 2006

Report for period 7 April to 13 April 2006

After 5 months of cruise phase Venus Express has been inserted into a Venus orbit on 11 April (DoY 101) at about 08:00 UTC with a successful burn of its Main Engine which has slowed down the spacecraft such that it could be captured by the gravity of the planet.

All operations leading to the burn and immediately after have been nominal both on the space and the ground segments.

Only 48 hours after the successful Venus Orbit Insertion (VOI) the first science data have been received on ground showing astonishing pictures of the planet. The spacecraft is now in a 9-day orbit during which 6 science observations are planned together with a Pericenter Control Manoeuvre and the first Apocenter Lowering Manoeuvre.

The table below shows a chronology of the main activities in the reporting period:

MET (Day) Date DOY Main Activity
150 07/04/06 097 VOI Commands Uplink
151 08/04/06 098 SC monitoring
152 09/04/06 099 SC monitoring
153 10/04/06 100 FDIR Run-down and SSMM Switch OFF
154 11/04/06 101 VOI Operations
155 12/04/06 102 Swap to HGA1 and 1st science observation (COB00)
156 13/04/06 103 2nd Science observation (COB01)

At the end of the last Cebreros pass in the reporting period (DOY 103, 13:00) Venus Express was orbiting Venus at 124 million km from the Earth and 108.6 million km from the Sun. The one-way signal travel time was 413 seconds.

Spacecraft Status

AOCS

The Main Engine has been successfully fired on DoY 101 for the capture burn. The commanded delta-V was 1251 m s-1.

Payload Activities

ASPERA
The instrument has been successfully operated as part of the COB01 observation.

MAG
The instrument has been switched ON on DoY 102 as part of the science operations for the capture orbit.

PFS
The instrument is OFF.

SPICAV
The instrument is OFF and will be operated for the next science observations during the capture orbit.

VeRA
The USO is kept powered but muted.

VIRTIS
The instrument has been operated on DoY 102 and 103 as part of the capture orbit operations. The quality of the data is judged very good. The instrument will be operated for all the 6 science observations of the capture orbit.

VIRTIS composite image of the Venusian south pole

The clarity of the cloud patterns in the VIRTIS IR image is absolutely astonishing, in particular when considering that the instrument detector has not yet reached its nominal cryogenic temperature and that the distance to the planet is between three and 100 times the distance when in the final orbit.

This VIRTIS image shows on the left the Sun-illuminated side of Venus at UV wavelengths, visualising streaks due to high speed winds at about 65-70 km altitude. On the right hand side the image shows the thermal radiation from the lower atmosphere penetrating the clouds at a wavelength of 1.7 μm. The structure is due to clouds at a level of 55-60 km where dense clouds block more radiation, resulting in darker colours and thinner clouds resulting in brighter colours. The dynamic structure of this part of the atmosphere is evident. The pixel size is 50 km.

VMC
The instrument has been operated on DoY 102 and 103 as part of the capture orbit operations. The quality of the data is being assessed. The instrument will be operated for all the 6 science observations of the capture orbit.

The VMC image shows the Sun-illuminated side of Venus, as seen from the south pole through a UV filter, both in false colour and greyscale. The pixel size is 150 km.

VMC false colour image

VMC greyscale image

The first Venus Express data received from the VIRTIS and VMC already shows that this mission will have a major impact on Venus research and Solar System research in general.

Ground Facilities

The Venus Express ground station network for VOI operations included the following stations:

  • ESA Cebreros
  • ESA New Norcia
  • DSN Madrid
  • DSN Goldstone
  • DSN Canberra
All sites have provided the required support with excellent performance. The S-band signal from the LGA has been successfully tracked by the DSN Madrid station (DSS-63) during the VOI burn providing real-time data on the progress and performance of the capture burn.

From now onwards Cebreros is the primary station for Venus Express with New Norcia and DSN stations providing support for Radio Science operations.

All ground segment systems performed nominally during the VOI operations.

Orbit Insertion Events

This is the detailed sequence of events as conducted in the 48 hours around the VOI capture burn.

DoY 100 - 10 April 2006
07.00 Solar Arrays repositioning for capture burn
10:00 Wake-up timers and HIBs setting
10:45 SSMM Switch OFF
19:05 Main Engine Boost Mode parameters setting for VOI burn
20:30 Last TC (ping) before VOI to reset TLMAP counter
DoY 101 - 11 April 2006
05:54 Slew to burn attitude started
06:24 End of slew to burn attitude - X-TX OFF
07:04:35 Switch to Main Engine Boost Mode - Burn Init Phase / Watch-dog inhibition
07:07:56 Liquid Settling Phase started
07:10:29 Main Engine burn started
07:45 Occultation start - loss of S-band signal at Madrid
07:55 Occultation end
07:57 S-band signal acquisition at Madrid
08:00:28 Main Engine burn end - Capture confirmed
08:10 AOCS FDIR partial re-activation
08:45 DMS FDIR partial re-activation
09:12 X-band TM reception at Cebreros and Madrid
10:15 Ephemeredes update
11:30 AOCS FDIR re-activation
12:00 Switch to AOCS Normal Mode
12:36 Switch ON of 4th Reaction Wheel
14:30 SSMM Switch ON and full configuration
17:00 TM storage enabled in SSMM
DoY 102 - 12 April 2006
02:00 Start slew to invert SC attitude - TTC Reconfiguration to HGA1
02:30 End of slew - RF link established via HGA1
04:00 USO surveillances enabling
05:40 Science observations COB00 and COB01 loaded

The first orbit determination has confirmed excellent performance of the main engine and the following deviations from nominal parameters:


    Period: +3.5 hours (~1.6%)
    Inclination error: 0.04°
The impact of these deviations is almost negligible.

Future Milestones

The spacecraft is now on the 9-day capture orbit which will be lowered with an Apocenter Lowering Manoeuvre of 199.86 m s-1 to be executed in the morning of 20 April. At the apocenter of this orbit (on 15 April) a Pericenter Control Manoeuvre of 5.8 m s-1 will be executed to set the pericenter altitude to the target value of 250 km. Science observations will be performed throughout the capture orbit for a total of 6 observations. The Venus Orbit Commissioning will start on 22 April and payload operations will be interleaved with orbit manoeuvres required to reach the target operational orbit on 7 May.


Last Update: 02 May 2006

For further information please contact: SciTech.editorial@esa.int

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