After a month-long hiatus from its routine scientific operations, 31-year-old Hubble Space Telescope (HST) is back in working condition and ready to resume its cataloguing of the stars. The telescope halted observations around mid-June, and NASA scientists have been working since then to bring everything back to 100% operation. As reported by Science, the first sign of a problem came from a system-monitoring payload computer which put the telescope’s instruments into safe mode after observing a communications error. NASA eventually determined that a power control unit (PCU) was the root source of the issue. The PCU is responsible for supplying a reliable amount of voltage to the payload computer, and the current PCU was failing to do so.
Fortunately, Hubble was launched into orbit with a significant supply of spares, including one for the payload computer and the PCU. NASA reported that the backup PCU was brought online to power the encompassing system, the Science Instrument Command and Data Handling unit, and the unit’s backup payload computer was then booted up with the relevant flight software. As all the backups were activated, “…Hubble was successfully recovered into Normal Mode…” according to Tom Brown, head of the Hubble mission office. Brown confirmed that Hubble could be back to making its cosmic observations this week.
Swapping to a spare and continuing its work, the HST is once again running the distance far beyond what anyone could have expected of it. Originally only supposed to last for 15 years, Hubble has provided astronomical knowledge and stunning visuals of space for twice its expected lifetime and will likely continue doing so for years to come. Brown spoke to Technology Review back in March, when the telescope went into safe mode due to a separate issue, saying that the HBT may last until “…at least 2026, and perhaps the whole decade….” Hubble has lasted so long because it is the first space telescope that was designed to undergo maintenance. It has had five shuttle missions for service and repair; though, it is unlikely to get another. Between repairs and a host of redundancies and backup hardware, Hubble has maintained working condition of all its major instruments. Even when one of the instruments finally fails for good, the others may continue working for several additional years.
By the end of the year, NASA aims to launch the James Webb Space Telescope (JWST). While the JWST will replace Hubble as NASA’s flagship space telescope, it will not be a direct successor because the JWST will mainly operate at different light wavelengths than Hubble does. Plus, Hubble will likely still be in full operation as the JWST heads into orbit. As time goes on, the Hubble Space Telescope will begin to come out of these technical errors and glitches without its full capacity. Eventually, all of its main instruments will fall into disrepair. But that horizon has not yet made itself visible, and Hubble pushes on full steam (or, more appropriately, full sun) ahead. With both the Hubble Space Telescope and the James Webb Space Telescope orbiting by the end of this year, our vision of the cosmos is about to get that much clearer.
Sources: Science; NASA & NASA; Technology Review
