Both instruments aboard NASA’s Fermi Gamma-ray Space Telescope have resumed science observations. The spacecraft itself is functioning well despite the March 16 failure of a mechanism that drives one solar panel, an event that triggered an automatic “safe hold” that powered down Fermi’s instruments.
The Gamma-ray Burst Monitor (GBM) was powered back up on March 28 and has resumed normal science operations, detecting more than two dozen gamma-ray bursts since. The GBM sees the entire sky not blocked by Earth.
Fermi’s primary instrument, the Large Area Telescope (LAT), was powered up on April 2 and allowed to reach its nominal temperature before observations resumed on April 8.
Currently, the observatory is using a slightly different strategy for viewing the sky. This strategy is still being optimized while the engineering team continues to study the cause of the anomalous solar panel behavior.
Since its return to duty, the LAT has detected numerous flares from active galaxies powered by supermassive black holes and saw two novas — stellar explosions occurring on white dwarf stars in our own galaxy.
“The gamma-ray sky has been quite active lately, so we’re glad the LAT is back on the job,” said Fermi Project Scientist Julie McEnery at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Media Contact: Felicia Chou, NASA Headquarters
March 30 Update
Early on March 28, the Gamma-ray Burst Monitor aboard NASA’s Fermi Gamma-ray Space Telescope was reactivated, returning the mission to partial science operations.
On March 27, Fermi was placed at a fixed angle relative to its orbit. This direction puts the most sunlight on a solar panel that stopped moving on March 16 and provides the spacecraft with the best power margin.
“We want to start things off in a conservative way,” said Fermi Project Scientist Julie McEnery at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We will stay at this angle for a while and monitor spacecraft performance, and then bring the Large Area Telescope back online over the next week.”
The failure of the solar array drive is the first problem tied to hardware that Fermi has experienced after nearly a decade in space. The cause of the failure remains under investigation.
Media Contact: Felicia Chou, NASA Headquarters
March 22 Update
At 1:11 a.m. EDT on March 16, NASA’s Fermi Gamma-ray Space Telescope encountered an issue with a drive on one of its solar arrays. This caused Fermi to automatically enter a “safe hold” mode, where its instruments are powered off and not acquiring science data. Initial investigation suggests that the affected solar panel is not moving when prompted. Investigation into the cause of the anomaly is ongoing. The Fermi team is exploring options to resume some science operations with a fixed (stationary) solar panel while the anomaly investigations continue. According to Project Scientist Julie McEnery at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, the team is planning to start a return to science operations next week, to run in parallel with the ongoing engineering investigation.
The problem is connected to the drive on one solar array, which failed to move as instructed in one direction. Fermi’s solar arrays move throughout its orbit to maximize the sunlight striking the arrays, which charge batteries that power the spacecraft. As of this writing, engineers do not understand why the drive is unable to move in one direction, and the affected panel remains stationary. Because Fermi was designed with a large power margin, the observatory may be able to continue observations indefinitely with one stationary solar array, and this option is being explored.
NASA’s Fermi Gamma-ray Space Telescope was launched on June 11, 2008, and has been functioning well throughout its near-decade in Earth orbit. Fermi began its extended mission in 2013 and has made significant contributions in gamma-ray astronomy, including seeing the first light from a gravitational-wave source just last year. Other contributions include detailed observations of titanic cosmic explosions known as gamma-ray bursts, most of which are thought to be powered by black holes formed inside collapsing stars, high-energy flares from distant galaxies called blazars, thought to be powered by supermassive black holes millions (and more!) times the mass of our Sun, and gamma-ray flashes associated with lightning on Earth.
Media Contact: Felicia Chou, NASA Headquarters