Space is Hard Work!

Pictures showing Sentinel-1A’s solar array before and after the impact of a millimetre-size particle on the second panel. The damaged area has a diameter of about 40 cm. Data courtesy of ESA>

Pictures showing Sentinel-1A’s solar array before and after the impact of a millimetre-size particle on the second panel. The damaged area has a diameter of about 40 cm. Data courtesy of ESA>

Space is unpredictable. Things don’t always go as planned. Over the last few weeks some of the difficulties of working in space have been highlighted.

Gaofen 10
The start of September did not go well for the satellite industry with two failed launches. Firstly, the Chinese Gaofen 10 Earth observation satellite launched on the 31st August onboard the Long March 4C rocket did not appear to have achieved its orbit. The lack of certainty about this is because no official announcement has been made by Chinese authorities, despite pictures of debris appearing on social media the following day. Gaofen-10 was believed to be carrying a multi-polarized C-band SAR instrument and was intended to be part of the China High-Resolution Earth Observation System (CHEOS), joining the existing seven orbiting Gaofen satellites to provide real-time global Earth observations.

SpaceX
The explosion of the SpaceX Falcon rocket on the Cape Canaveral Launchpad received significantly more mainstream media attention than Gaofen 10. This was partly due to the fact it was a SpaceX rocket, and partly because the satellite it carried was going to be used by Facebook. When you have two of the US’s most well-known technology gurus involved, it was bound to grab the headlines.

No-one was hurt, but the satellite was destroyed by the explosion that occurred whilst the rocket was being loaded with fuel; investigations continue into the cause of this. It was an Israeli communication satellite called Amos 6, whose main purpose was the delivery of television channels. However, Facebook also had an agreement to use the satellite to provide internet connectivity to sub-Saharan Africa.

Sentinel-1A Struck in Space
ESA recently confirmed that the Copernicus Sentinel-1A satellite was hit by a millimetre-size particle on one of its solar wings on the 23rd August. The impact caused slight changes to the orientation and orbit of the satellite, although it hasn’t impacted performance.

Engineers were able to activate the onboard cameras, which provided a clear picture of the impact site on the solar panel, which can be seen in image at the top of the blog. The damaged area is approximately 40 centimetres wide, which is consistent with the impact of a fragment of less than 5 millimetres. This damage has reduced the power generated by the solar wing, although the loss will not impact performance as current power generation remains higher than what the satellite requires for routine operations.

It’s not clear whether Sentinel-1A was stuck by space debris or a micrometeoroid. Given the amount of space debris up there significantly larger than 5 millimetres, the potential damage that could be done to satellites is massive!

Back in STEREO
On a more positive note, last month NASA re-established contact with a satellite after a gap of almost two years. In 2006 NASA launched a pair of twin Solar TErrestrial RElations Observatory (STEREO) satellites to provide data about the sun’s solar flares and coronal mass ejections. Contact was lost with STEREO-B (so called because it was orbiting behind STEREO-A; the A signified it was ahead!) on the 1st October 2014 during a routine test. Since that time NASA has been working to re-establish contact with STEREO-B, and amazingly did so on the 21st August 2016!

Having made contact the team are assessing the satellite, and its components, with the hope of bringing it back to working order in the near future.

Close-up of the Philae lander, imaged by Rosetta’s OSIRIS narrow-angle camera on 2 September 2016 from a distance of 2.7 km. The image scale is about 5 cm/pixel. Philae’s 1 m-wide body and two of its three legs can be seen extended from the body. Image courtesy of ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.

Close-up of the Philae lander, imaged by Rosetta’s OSIRIS narrow-angle camera on 2 September 2016 from a distance of 2.7 km. The image scale is about 5 cm/pixel. Philae’s 1 m-wide body and two of its three legs can be seen extended from the body. Image courtesy of ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/ INTA/UPM/DASP/IDA.

Philae Located!
A second discovery after lost contact is ESA’s Philae Lander! This was the robot that made a historic landing on Comet 67P/Churyumov–Gerasimenko in November 2014, as part of the Rosetta mission. Unfortunately, Philae bounced away from the intended landing site and after a short period of operation, communications were lost. There was brief resurrection in July 2015, before silence returned.

Amazingly, last week the resting site of Philae was finally located with Rosetta’s high resolution camera. It is stuck in a dark crack on the comet surface, explaining why its solar powered batteries were unable to be recharged.

Philae will be joined later this month by the Rosetta probe itself, as it will be crash landed onto the comet. Cameras and chemical sensors will be operating throughout the descent which is planned to take place on the 30th September bringing to end this historic comet chasing mission.

Onward Despite Difficulties
DigitalGlobe’s WorldView 4 satellite is due to be launched on Friday, 16th September aboard an Atlas V rocket from Vandenberg Air Force Base. Like WorldView 3 this satellite should provide imagery with a spatial resolution of 31 cm in panchromatic mode and 1.24 m in multispectral mode.

This shows that despite all of the ups and downs of the last few weeks, the satellite industry keeps moving forward!

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