After more than a month of testing, NASA engineers have finally diagnosed the source of the problem on Hubble, the 31-year-old giant telescope that currently orbits space nearly 600 kilometers from Earth.
On June 13, Hubble automatically put all of its scientific instruments to sleep as a safety measure after the telescope’s payload computer failed. This computer is one of the central systems that controls and coordinates the instruments on board the spacecraft and transmits scientific and technical data to the ground.
Hubble out of service for a month
This means that Hubble’s instruments have been out of service for a month and the telescope is not recording any data. Hubble was launched in 1990 to observe the stars and galaxies in the universe. Normally, it transmits around 150 gigabits of raw scientific data every week.
So NASA engineers worked at a steady pace to restore the telescope’s instruments, but identifying the exact source of the problem from a distance proved difficult.
The payload computer is located in a specific Hubble unit called the Scientific Instrument Data Processing and Control Module. This is responsible for synchronizing all of Hubble’s science systems, as well as processing, formatting, storing and transmitting data to the Earth-based NASA team.
Engineers quickly determined that the problem was not directly related to the payload computer, but rather was caused by another component. They have now discovered that the culprit is most likely the power control unit, which supplies power to the payload computer hardware.
The power control unit consists of both a power regulator, which supplies a constant five-volt electrical voltage to the payload computer, and a secondary system, which checks the levels of voltage coming out of the power regulator and tells the computer to stop working if there is a problem with the amount of electricity being supplied.
Two scenarios have arisen: either the power regulator sends out wrong voltage levels, which causes the secondary system to crash the payload computer, or the secondary system itself fails and needlessly keeps the computer offline. .
Find a needle in a haystack … from a distance
It took a long time for NASA to come to this conclusion. Scientists at the organization initially thought the issue was with the payload computer itself, and tried turning on the device’s rescue system, but faced the same symptoms. .
It was then that the team realized that the source of the problem had to be found in another hardware component. But finding out which component exactly, hundreds of miles away, was like finding a needle in a haystack. In the space.
Unlike what would have happened if Hubble was in a lab, NASA engineers couldn’t play with the components to test different hypotheses. Instead, they had to patiently examine all possible causes, sending specific commands to the telescope to check if it was responding normally, until they found the problematic component.
A risky operation
Although the Hubble team has now identified the Power Control Unit as the source of the problem, this is only the start of the repair. It is not possible to reset the component using ground controls, which means the NASA team will have to switch to the back-up system of the module that contains the back-up control unit.
This is a complex and risky operation, as it is likely to impact several other satellite devices, which are also connected to this power control module.
“Every time we change components in the operational chain, we treat it as a big deal,” Paul Hertz, director of NASA’s astrophysics division, told ZDN. “We want to make sure that we are doing it correctly, that we think about all the possible consequences of this change, that we send the correct commands to the satellite, so that it performs the exchange correctly and safely. “
Advance with caution
Since the beginning of July, the Hubble team has been preparing for the switchover. The process involves preparing for a test of procedures, followed by several days of testing, as well as a review to assess any risks associated with switching to a standby device.
“We have well-established processes, where the team first reviews the procedures, makes sure they are correct and do not require updates, and then designs the file to upload. This is examined by an independent team which gives the final decision to accept or refuse, ”explains Paul Hertz.
“No matter how simple or complex the change is, we have a thorough process to make sure we are careful. “
A first failure had been repaired remotely
The change will be made over the next few days, and NASA engineers hope the operation will allow Hubble to resume normal scientific observations as quickly as possible.
Part of the confidence of the Hubble team comes from the fact that this is not the first time that the space observatory has needed a remote repair. In 2008, the telescope experienced a failure related to another component, which prevented the system from transmitting information to Earth.
A backup has been activated successfully and Hubble has restarted. The first image released by the observatory after a month-long hiatus showed one galaxy passing through the heart of another, 400 million light years from Earth. Something to celebrate in the coming weeks, once Hubble is up and running again.