sci21006 — Announcement
Hubble’s Summer 2021 Journey
11 October 2021
-By Paule Sonnentrucker-
This summer Hubble kept us all on the edge of our seats again! This time it was not only because it continued to reveal new, breathtaking views of our Universe, but also because Hubble had to weather its own health issues that brought science observations to a halt for the best part of five long weeks.
In the afternoon of Sunday 13 June 2021 the payload computer on board Hubble halted and the spacecraft stopped collecting science observations. The telescope and all active instruments successfully entered their respective safe mode configurations, where they remained in good health throughout the duration of the investigation and until the recovery of Hubble to science operations on 17 July 2021.
The Hubble payload computer’s role is to control and coordinate the science instruments. It also monitors the instruments for health and safety purposes. This system, built in the 1980s, resides in the Science Instrument Command & Data Handling (SI C&DH) unit, which was replaced during Servicing Mission 4 in 2009.
There are various pieces of hardware that make up this unit. The Hubble teams at GSFC and STScI therefore embarked on a series of multi-day tests which included attempts to restart and reconfigure the computer and to isolate the cause of the halt.
These complex tests took place through the end of June. While the team’s attempts to restart the payload computer were not successful, the information they gathered indicated that the possible cause of the failure was linked to a power regulator in the Power Control Unit (PCU). The problem appeared to be linked to the fact that Hubble had been operating on Side B since the last servicing mission in 2009. The safest possible way to restart science activities was to switch to Side A. Switching the sides involves complex procedures, but these are well documented, tested, and rehearsed.
On 15 July, following a thorough review and formal approval by NASA management, the Hubble world stood still and held its breath as the Hubble team successfully performed the critical switch to Side A. This involved powering-on the payload computer on Side A, monitoring the hardware, and finally initiating the processes for recovering the science instruments out of their safe mode configurations. We were all then able to breathe a sigh of relief. “Hubble is back!” announced the team.
Since 17 July Hubble science operations have returned to nominal operations. The performance of all instruments is nominal and on a par with pre-safing conditions and Hubble’s return was celebrated with a beautiful view of the Oddball Galaxies. Hubble is back to its old resilient self, gathering new data and ready for the next groundbreaking discoveries, thanks once again to the dedication, ingenuity, and resilience of the staff at GSFC and STScI (new and alumni!) who worked tirelessly on the investigation and recovery of this unique observatory.
