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No. 237 - Superior Solar Conjunction

No. 237 - Superior Solar Conjunction

Report for the period 17 July to 27 August 2011 (week 29 - week 34)The reporting period covers six weeks of Venus Express mission operations, rather than the usual four. During this period, routine planned operations at very low downlink data rates were carried out, followed by the transition into and the duration of Superior Solar Conjunction. During Superior Solar Conjunction spacecraft operations are reduced to a minimum.

Summary of main activities

The reporting period began with routine science activities and was nominal on the spacecraft side.

Orbit Change Manoeuvres (OCM) were executed on 17 July (at pericentre) and 18 July (apocentre) 2011.

The solid-state mass memory (SSMM) had a re-occurrence of an anomaly on 25 July 2011 causing the telecommand file transfer to be aborted. The unit was recovered by executing a warm reset.

The Earth-spacecraft-Sun alignment approached Solar Conjunction, when the Sun is almost directly between the spacecraft and the Earth. The angle, from the Earth to Venus to the Sun, is between 3 degrees and 6 degrees. This places a powerful energy source (the Sun) almost directly in the line from the Earth to the spacecraft, with the result that it can be harder to detect the spacecraft downlink signal, and harder to get a clear signal to the spacecraft from Earth. To offset the problems caused by this situation, the Telemetry and Telecommand bit rates (TLM BR and TC BR) were decreased on 26 July before entering the Solar Conjunction operations. As a general rule, reducing the amount of information in the signal increases the signal clarity. The Cebreros ground station also switched from the usual downlink power amplifier (the X-Band Low Power Amplifier, or XLPA) to the High Power Amplifier (XHPA), to improve the raw signal strength, and therefore the ease of signal detection on the spacecraft.

On 05 August 2011, all science operations were stopped due to the upcoming loss of communications (during Solar Conjunction). On 06 August, Venus Express entered Superior Solar Conjunction; this lasted until 26 August. Science operations were resumed on 28 August.

The spacecraft functioned autonomously without ground control from 08 August to 22 August to allow maintenance at the Cebreros (CEB) ground station. During this period, two short passes, on 10 August and 18 August and each of 3 hours duration, were held with the New Norcia (NNO) ground station, to check the spacecraft status. Daily passes resumed on 22 August through the nominal ground station at Cebreros.

Main activities during reporting period

MET
(Day)

Date
(DD-MON-YYYY)

DOY

Main Activity

MET = Mission elapsed time; DOY = Day of year

2077 17-Jul-2011 198 CEB communications pass. OCM at pericenter
2078 18-Jul-2011 199 CEB communications pass. OCM at apocenter
2079 19-Jul-2011 200 CEB communications pass.
2080 20-Jul-2011 201 CEB communications pass.
2081 21-Jul-2011 202 CEB communications pass.
2082 22-Jul-2011 203 CEB communications pass.
2083 23-Jul-2011 204 CEB communications pass.
2084 24-Jul-2011 205 CEB communications pass.
2085 25-Jul-2011 206 CEB communications pass. SSMM warm restart.
2086 26-Jul-2011 207 CEB communications pass. TLM and TC bit rates decreased.
2087 27-Jul-2011 208 CEB communications pass.
2088 28-Jul-2011 209 CEB communications pass.
2089 29-Jul-2011 210 CEB communications pass.
2090 30-Jul-2011 211 CEB communications pass.
2091 31-Jul-2011 212 CEB communications pass.
2092 1-Aug-2011 213 CEB communications pass.
2093 2-Aug-2011 214 Short CEB communications pass due to maintenance.
2094 3-Aug-2011 215 Short CEB communications pass due to maintenance .
2095 4-Aug-2011 216 CEB communications pass.
Uplink of conjunction on-board commands
2096 5-Aug-2011 217 CEB communications pass.
Science operations stopped before CEB acquisition of signal (AOS).
2097 6-Aug-2011 218 CEB communications pass
Solar Conjunction start. CEB began using the X-Band High Power Amplifier (XHPA) with an uplink power of 7kW.
2098 7-Aug-2011 219 CEB communications pass. First day after entrance into Superior Conjunction. Telemetry downlink bit rate at 297 bps, telecommand uplink bit rate at 250 bps.
2099 8-Aug-2011 220 CEB communications pass.
2100 9-Aug-2011 221 CEB Maintenance. No pass.
2101 10-Aug-2011 222 CEB Maintenance. No pass.
2102 11-Aug-2011 223 Short NNO pass. Spacecraft status OK.
2103 12-Aug-2011 224 CEB Maintenance. No pass.
2104 13-Aug-2011 225 CEB Maintenance. No pass.
2105 14-Aug-2011 226 CEB Maintenance. No pass.
2106 15-Aug-2011 227 CEB Maintenance. No pass.
2107 16-Aug-2011 228 CEB Maintenance. No pass.
2108 17-Aug-2011 229 CEB Maintenance. No pass.
2109 18-Aug-2011 230 Short NNO pass. Spacecraft status OK.
2110 19-Aug-2011 231 CEB Maintenance. No pass.
2111 20-Aug-2011 232 CEB Maintenance. No pass.
2112 21-Aug-2011 233 CEB Maintenance. No pass.
2113 22-Aug-2011 234 CEB communications pass.
2114 23-Aug-2011 235 CEB communications pass.
2115 24-Aug-2011 236 CEB communications pass.
2116 25-Aug-2011 237 CEB communications pass.
2117 26-Aug-2011 238 CEB communications pass. Conjunction exit operations. Telemetry bit rate to 57 kbps, telecommand uplink bit rate to 1000 bps. CEB resumed nominal use of the X-Band Low Power Amplifier (XLPA).

At the end of the reporting period on 27 August 2011, Venus Express was at 258.09 million kilometres from Earth. The one-way signal travel time was 860 seconds.

At the end of the reporting period, the final oxidizer mass was estimated to be 32.391 kilograms, and the final fuel mass estimate was 20.178 kilograms.

Payload Activities

ASPERA The instrument was regularly operated as part of the routine plan, except during the Superior Solar Conjunction period.
MAG The instrument was regularly operated as part of the routine plan, except during the Superior Solar Conjunction period.
PFS The instrument was not operated.
SPICAV The instrument was regularly operated as part of the routine plan, except during the Superior Solar Conjunction period.
VMC The instrument was regularly operated as part of the routine plan, except during the Superior Solar Conjunction period.
VeRa The instrument was not operated
VIRTIS The instrument was regularly operated as part of the routine plan, except during the Superior Solar Conjunction period.

Future Milestones

  • Atmospheric Drag Experiment (ADE) #6 will start on 13 September 2011.
  • Atmospheric Radio Occultation (OCC) season #12 begins on 15 November 2011


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This report is based on four ESOC mission operations reports, MOR #297 through MOR #300. Please see the copyright section of the legal disclaimer (bottom of this page) for terms of use.

    Last Update: 1 September 2019
    13-Aug-2020 02:11 UT

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