About this ArticleJ. MacKenty (mackenty[at]stsci.edu)
The Hubble Space Telescope continues to perform its science program despite a few glitches over the past months. April 24 was Hubble's 32nd birthday! Testimony is seen in the beautiful anniversary image (Fig. 1). Demand for observing time remains strong with over 1,000 proposals received for Cycle 30 and over 1,000 new papers using Hubble data published in 2021, with 35 associated press releases. Hubble maintains its exemplary record with research results ranging from the circulation pattern of Jupiter's dynamic atmosphere and other solar system phenomena to nebula, star-formation regions, exoplanet atmospheres, and pushing to the limits probing the cosmos.
Our response time for minor issues remains outstanding. For example, on April 5 a so-called single-event upset (SEU) halted the Cosmic Origins Spectrograph's internal computer. This was caused by a charged particle from the South Atlantic Anomaly during one of HST's 7–8 daily transits through that concentration of trapped electrons and protons. No harm was done to COS. The event occurred about 10:30 in the evening and science operations resumed at 1:48 p.m. the next day, avoiding the loss of any scheduled science observations.
Two more significant issues impacted HST observations during the past year. In late October 2021, a synchronization signal dropout between the spacecraft and payload computer (which controls the science instruments) stopped science observations. We initially resumed only ACS observations and then restarted the other instruments when this event did not recur. Hard work by the flight software teams created, tested, and installed patches to mitigate this behavior should it recur in the future. The patches were applied on December 21 (COS, February 4 (WFC3), February 15 (STIS), and March 2 (ACS) while normal operations continued. These patches protect against a possible repeat of the October dropped sync signal, which has the undesirable consequence of safing the instruments.
In general, HST retains considerable depth of redundancy in its hardware components. One important exception is the Science Instrument Command and Data Handler (SI C&DH) computer (i.e., the payload computer). The "Side B" of this unit (used since its installation in 2009 during Servicing Mission 4) suffered an electronic fault last summer. After extensive tests to isolate the fault, operation was switched to the backup side ("Side A") and nominal operations have continued since then. Further analysis has determined that operation of the science instruments is possible using Side B with various restrictions and significant software modifications. Efforts to develop this software are underway to restore redundancy in this system.
HST science will remain strong in concert with the long-awaited initiation of JWST observations.