NASA has finally figured out what caused the payload computer failure that took the Hubble Space Telescope out of operation on June 13th. In a note released this Wednesday (14), the agency revealed that the problem could be in the Energy Control Unit (PCU).
Located in the ship’s Scientific Instrument Command and Data Handling unit, the PCU is responsible for the constant supply of power. It contains a voltage regulator that provides five volts of electricity to the payload computer and its memory.
In case of part failure, with the voltage being above or below the permitted levels, a secondary protection circuit comes into action, causing the device to stop functioning. Analyzing the situation, the American space agency believes in two hypotheses.
Either the voltage level of the regulator is outside of acceptable standards, disabling the equipment for safety, or the secondary circuit has degraded over time. In the latter case, the system would also cause the computer to be “stuck” in this inhibited state, according to NASA.
Fixing the problem
Restarting the PCU was one of the ways to fix the Hubble bug, but the mission controllers were unable to carry out the procedure via ground commands. So they decided to switch to the telescope’s backup hardware, which also has a backup power unit.
The exchange should start this Thursday (15) and, if successful, the forecast is that the system will return to work correctly in a few days, resuming normal scientific operations. The process is similar to that which occurred in 2008, when another payload computer component failed.
In orbit since 1990, the Hubble telescope has made more than 1.5 million observations of the universe, contributing to some of the major scientific discoveries of recent decades.