Inara Pey: Living in a Modemworld

NASA has successfully restored the Hubble Space Telescope (HST) to full operations after more than a month with the telescope either being in a “safe” mode, or only able to partially operate its science instruments.

The longest-running space mission in Earth orbit, HST has been subject to a range of issues throughout its career, all of which have been overcome, although this has been only of the more draw-out in getting resolved. It started on October 23rd, when the telescope started sending error codes indicating the loss of a specific synchronisation message that provides timing information used by its instruments use to respond to data requests and commands correctly. Two days later, the same error codes were again issued, prompting Hubble to cease science activities and enter a “safe” mode.

Throughout out the rest of October and early November, mission engineers on Earth worked to diagnose and rectify the issue, and on November 8th, 2021, were able to report a restart of the main computer system and a set of back-ups had allowed science operations to recommence on the telescope’s Advanced Camera for Surveys (ACS). Later in November, operations were restored to the Cosmic Origins Spectrograph (COS) and then the Wide Field Camera 3 (WFC-3), Hubble’s most heavily-used instrument, leaving just one major science instrument out of commission.

That was the Space Telescope Imaging Spectrograph (STIS),  which was finally restored to operational status on Monday, December 6th, marking Hubble’s full return to its science programmes.

However, the October glitch, following on as it does from a systems error that caused the telescope to enter a safe mode in July 2021, serves as a reminder that HST is running on software and systems designed and built in the 1980s.

As a result, the mission team has been evaluating and testing ways and means to refine and update the telescopes software on both its operating systems and its science instruments. This means that mid-December should see the COS gain a significant software update, with the remaining science instruments also being updated early in 2022.

Such upgrades are vital to Hubble’s continued career, given there has been no means to physically service it since the space shuttle was retired in 2011 – and NASA / ESA very much hope to keep the observatory running through until at least the end of the 2030s, consumables permitting.

That said, and if all goes according to plan, Hubble will so no longer be the only large-scale, space-based observatory in operation.

As I’ve frequently reported in these pages, the James Webb Space Telescope (JWST) is due to be launched from the European Spaceport, Kourou, French Guiana, on December 22nd, 2021. This is actually 4 days later than planned, the result of unexpected vibrations passing through the telescope after a clamp unexpected released as JWST was being integrated with the Launch Vehicle Adapter (LVA) – the element that physically connects the telescope to the rocket. This required a period of checks to be carried out to confirm the telescope’s instruments and systems had not been damaged by the vibrations.

However, following confirmation that no damage had been caused, two of the four remaining pre-launch operations for the telescope have now been completed and a third is in progress.

On November 23rd, European Space Agency engineers started the delicate operation to fill JWST’s propellant tanks with 168 kg of highly toxic hydrazine gas and 133 kg of equally toxic dinitrogen tetroxide oxidizer, both of which are needed to power the observatory’s thrusters. So harmful are both of these propellants, the loading took a total of 10 days, during which time engineers working in the same space as the telescope had to wear  Self-Contained Atmospheric Protective Ensemble (SCAPE) suits – essentially space suits for use on Earth that completely isolated them from their surroundings.

With fuelling completed on December 3rd work then commenced on bringing both the telescope, mounted on its LVA, and its Ariane 5 launch vehicle together for the first time, moving both of them into the Final Assembly Building and readying them for mating together. This work was completed on December 7th, 2021, clearing the way for the mating process to commence.

Mating involves lifting JWST and its LVA up to the high bay of the building, and then lowering it on to the top of the Ariane booster. Once this has been done, a final series of tests on telescope, LVA and booster will be carried out and the Ariane payload fairings will be closed around the telescope. After this, a final check-out will take place, and the final pre-launch activity will see booster and payload moved to the launch pad a few days ahead of the launch.

The launch itself will in turn mark the start of the most complex deployment of a space instrument undertaken to date. It will take JWST 16 days to reach its operational halo orbit at the Earth-Sun L2 point, with the entire deployment taking some 29 days, as the video below explains.

Continue reading “Space Sunday: telescopes, wings and exoplanets” →