Artists impression of. Sentinel-1 satellite. Image Courtesy of ESA/ATG medialab
We’re all dressed in black this week as we mourn the loss of three satellites:
EOS-02 & AzaadiSAT Satellites
In our previous blog we wrote about the planned launch last weekend of the EOS-02 & AzaadiSAT satellites by the Indian Space Research Organisation (ISRO) via its Small Satellite Launch Vehicle (SSLV). The launch took place, as expected, over the weekend and the first three stages went well, but during the final fourth stage ISRO reported a loss of data from the rocket. A few hours later they announced the launch had failed to deliver the satellites into their intended orbit, due to a sensor failure and it was not detected in time to take mitigating action.
Rather than being placed in the planned circular orbit, the sensor failure caused the satellites to be put into an elliptical orbit. At its narrowest point, this orbit left the satellites just under 50 miles from Earth, and reports are that the satellites have already reentered the Earth’s atmosphere over the Pacific Ocean.
ISRO were keen to emphasise that this was the first test flight of SSLV, and that many new elements of the rocket had worked well. They believe they know where the issue arose, but have instigated an investigation to understand what happened and correct this before the next test flight.
All satellite losses are unfortunate due to the time, effort and cost required to put them into orbit, although this one feels particular sad as the AzaadiSAT was designed and built by 75 female students across India to promote woman in STEM.
Sentinel-1B Satellite
Last week, the European Space Agency (ESA) sadly announced the end of Sentinel-1B. We had written earlier this year about the fact that the satellite had suffered an anomaly, just before Christmas, to its instrument electronics power supply meaning the satellite was unable to collect data. ESA engineers had tried a number of times to resolve the issue, but it’s Anomaly Review Board (who knew such a thing existed, but apparently it does) determined that it was now ‘impossible to recover the 28V regulated bus of the satellite’s C-band synthetic aperture radar antenna power supply unit, which is needed to provide power to the radar electronics.’
This announcement brings to an end the six year mission of Sentinel-1B, which was launched on the 25th April 2016. It was launched two years after its twin, Sentinel-1A – which is still operating as expected, and carried a C-band Synthetic Aperture Radar (SAR) instrument. It had a seven year planned mission life, although often satellite missions go beyond their planned end-of-life.
The loss of Sentinel-1B significantly reduces the frequency of available SAR data, although ESA is using Copernicus Contributing Missions to fill this gap to support the delivery of some Copernicus Services. The missions contributing date include Canada’s Radarsat-2 and Radarsat Constellation Mission, Germany’s TerraSAR-X, Italy’s COSMO-SkyMed and Spain’s PAZ.
Ultimately, the resolution to the situation will be the launch of Sentinel-1C, which has been brought forward and is now expected to go into orbit sometime between April and June next year.
ESA is also making plans to deorbit Sentinel-1B to ensure that inactive satellites are not left in space. When the satellite was launched the plan was that re-entry would take place within 25 years, which was the requirement at the time. Whereas now they expect it will happen much quicker, but no details available yet on exactly when this will occur.
Summary
The sad demise of these three satellites reminds us that working in space is hard difficult work, and when things go wrong it can be impossible to fix them.
