. Since then, the observatory has been sitting idle in a protective safe mode, while engineers on the ground are working to diagnose the problem and come up with a fix.. Hubble has suffered many technical failures in its past, and engineers have always managed to come up with clever fixes and workarounds to keep the spacecraft going. That’s, partly because Hubble has many redundant systems on board, but it could also be repaired by the space shuttle which made Five servicing calls to the observatory since 1993., But Hubble’s last servicing mission was in 2009. NASA retired its space shuttles. Just two years later, In April 2021, Hubble celebrated its 31st year on orbit. That’s, an incredible milestone, but it’s also a reminder of just how old, the Hubble Space, Telescope, is. And naturally, that has people wondering if mission engineers can fix this iconic but aging observatory.. Welcome to Launch Pad I’m Christian Ready, your friendly neighborhood astronomer.. Now. As of this filming Hubble’s mission operations, team are still trying to determine the exact problem and have already tested some possible fixes., It’s quite possible that by the time you watch this video Hubble will either have been returned to service or not at least not yet.. So what happened to Hubble and how do they know what the problem is and how they might fix it And what, if it can’t, be fixed from the ground? Well, today, we’re going to answer those questions, but first I’d like to thank Magellan TV who are sponsoring today’s video.

. If you’re a fan of Hubble, then I invite you to check out quotHubble’s Enduring Legacyquot a documentary about the iconic telescope’s history and what it has revealed about our universe over the last three decades.. This documentary and many more like it are available on Magellan TV, which is a new streaming service founded by the filmmakers themselves.. You can enjoy content on topics such as art, nature, history and, of course, space and science., And now Magellan TV is offering my viewers 30 off an annual subscription. That’s a full year of Magellan for just 3.50 a month Simply visit the link in the description to Claim your discounted membership today. On June 13th Hubble’s payload computer halted operations shortly after 400 p.m. Eastern Time., This isn’t, the spacecraft’s main computer, but rather a separate payload computer that’s responsible for coordinating and controlling the science instruments.. Normally, the payload computer sends a routine quotkeep alivequot signal to the spacecraft’s main computer. When the main computer stop receiving the signal it automatically suspended science operations and put the spacecraft into a safe mode., Exactly how Hubble safes itself depends on the situation. If there’s a malfunction That doesn’t otherwise threaten the telescope survival. It simply stops all science operations, puts the instruments on standby and maintains whatever pointing it was in at the time., But if the problem has to do with its power or pointing control systems, the computer then takes the additional step of commanding the solar arrays to directly Face the Sun to generate maximum power.

. Both of these safe modes are controlled by the main computer, but if the main computer were to have a problem or if its pointing system were to fail, another subsystem called the PointingSafemode Electronics Assembly or PESA takes command of the spacecraft.. The PESA computer turns off all unnecessary equipment to conserve power and angles: the solar arrays to face the Sun.. The system even has its own gyroscopes and pointing control system to move the telescope. If necessary., The system can even close the aperture door should the telescope drift to within 35 degrees of the Sun.. Now I tell you all this just to give you an idea of just how robust Hubble safing system is. It’s not going anywhere and it’s, not spiraling out of control or anything.. I don’t know the exact safe mode configuration Hubble is in right now, but its main computer power and pointing systems are all healthy and safe.. So my guess is: Hubble is probably in one of the quotlower tierquot safe modes, controled by its main computer. And that’s, exactly where we want it to be so the engineers can work the problem.. Now the payload computer is part of the Science Instrument Command and Data Handling unit or SI CampDH or, as I call it, quotSI C D Hquot.. This units stores and controls commands received by the science instruments formats the science data and sends it to the communication system for transmission to Earth., And this unit was replaced during the last servicing mission in 2009.

. It’S installed inside the door of one of the servicing bays that sits atop the science instruments. Its payload computer consists of a NASA Standard, Spaceflight Computer with two central processor modules, two standard interface circuit boards and four memory. Modules. The rest of the SI CampDH includes a redundant pair of command unit and science data for matters a pair of remote interface units that connect to the science instruments. And a power control unit with redundant power. Regulators, as well as various memory data and command communication lines called quotbussesquot that are connected by couplers.. These components are all redundant, so the system can recover from any single failure.. Initially, it seemed that the payload computer was unable to read to or write from memory. The mission’s operation team tried restarting the computer the next day and it ran for a little while, but it soon experience the same memory problem.. Each module has 64 kilobytes of memory.. Yes, I know 64 kilobytes., But remember we’re, talking about a computer that was designed in the 1980s and has to be hardened against radiation damage. Anyway. The payload computer uses only one of the four memory modules at any time., So the team tried to switch to one of the three back up memories., But the command to initiate a backup memory module failed to complete as well.. Then they tried to initiate both memory modules on the following day., But those attempts didn’t work either., And this suggested that the memory issue was really a symptom of a problem elsewhere in the SI CampDH.

. So the team began to investigate whether the payload, computers, central processing module or its interfaces could be at fault.. They switched on the backup computer for the first time in space.. Both computers have full access to the four memory modules.. However, it seemed that no matter which combination of computers and memory modules they tried the same problem kept coming back over and over again.. Now the odds of both computers and all for memory modules having degraded together, seems vanishingly small., Which means that the problem is probably further up. The hardware chain. Attention turned to the Command Unit: Science, Data Formatter or CUSDF, and the Power Control Unit.. The CUSDF is the module that routes commands to the science instruments and receive science data back and then formats the data for transmission to the ground., The Power Control Unit houses, a redundant pair of power regulators to ensure a steady voltage for the payload computer.. If the voltage is too high or too low, it could cause the computer to fail.. Now. The good news is that these electronics are also fully redundant with the primary on the SI CampDH’s quotA sidequot and the backup on the quotB sidequot., But switching to the B side, isn’t, nearly as straightforward as the switch is attempted on the computer. And that’s. Because of the way, the other hardware units elsewhere on the spacecraft are physically connected to the SI CampDH.. If they change to the B side, then those external units would also need to be switched over to talk to the B side as well.

, And that makes the switch procedure a lot more complicated and let’s face it. A lot riskier as well. Any time you make a change, there’s, always a risk of something going wrong., And this new procedure requires several changes to be made in a specific sequence.. However, this wouldn’t be the first time NASA had to perform this type of switch.. Remember when I said that this SI CampDH unit was replaced in 2009 Well that’s, because the previous unit had to be switched to its B side after it failed in September 2008.. As a matter of fact that final servicing mission was supposed to launch in December. Of that year, but it was pushed back by six months just so they could get the spare SI CampDH ready.. Now, whenever there’s a major switch like this, the mission operations team will take their time to make sure that everything is thoroughly reviewed and tested before taking any further action on the spacecraft. That’s. Why they spent the last week of June just reviewing and updating the procedures for the switch.. They even brought a high fidelity simulator out of mothballs and tested it out before they began testing the switch procedures. On July 8th the mission operations team successfully completed two days worth of testing of the switch procedures. That’s great news, but there’s also further scrutinizing of the Telemetry to make sure that they know exactly where the fault is. They don’t want to perform the switch.

If the fault really is somewhere else entirely.. But if everything goes well with the reviews they could perform. The switch in the coming week. Now it’s tempting to lament the fact that there are no more space shuttles left to service Hubble., But the truth is that Hubble goes into safe mode, a couple of times every year.. In fact, Hubble went into safe mode as recently as March, 7th of 2021 due to a software bug and you didn’t even notice. And that’s, because the mission operations team always takes the time they need to troubleshoot and diagnose the problem before they make a fix.. Some fixes are relatively easy, while others are more complicated. That’s the nature of running a space, telescope. quotButquot, you might say, quotHubble isn’t, just another space, telescope it’s OUR space telescopequot, And I would absolutely agree with you, but it’s, not the only one that we own. The Chandra X, ray Observatory, the Gehrels Swift Observatory and indeed every other NASA mission quotbelongs to usquot., And all of these telescopes have had safing events at one point or another.. In fact, they’ve had several. And sometimes they’ve lasted for up to months at a time. Plus those telescopes were never ever serviced on orbit.. However, Hubble is 31 years old and there’s no question it’s, showing its age. It’s NICMOS instrument, degraded to the point where they had to turn it off years. Ago. It’s pointing control system has run out of spare gyroscopes and now a critical subsystem is about to lose its primary electronics.

. Yes, the James Webb Space Telescope is touted as Hubble’s successor, but JJWST is an infrared. Telescope. Hubble is an optical, visible, light telescope that still outperforms the largest optical telescopes on the ground. That’s. Why astronomers still compete every year for time on Hubble., So yeah? It would be really nice if there was some way to support future servicing missions. NASA’s space, launch system and SpaceX’s Starship could certainly carry the payload necessary for a full shuttle style servicing mission., But both would require extensive modifications to actually carry that mission. Out. And those modifications could probably take several years on their own. I’ve, even wondered if SpaceX’s Crew Dragon could be modified to carry out a small, limited scope, servicing mission instead., But the more I think about it. The more I realize that this idea is not very straightforward. At all., A Crew Dragon would need a lot of modifications to support EVAs such as Sutt storage., The ability to open the side door from the inside docking with the soft capture mechanism, external handrails, a remote manipulator arm, etc. It would be great if we could send A robotic servicer that could dock with Hubble and repair it.. In fact, NASA’s started looking into the Hubble, Robotic Vehicle and Deorbit Module concept in the mid 2000s after the White House canceled Servicing Mission 4 in 2004.. This all occurred following the loss of the space shuttle Columbia, the previous year., So NASA’s Goddard Space Flight Center and some private companies teamed up to investigate the feasibility of servicing Hubble robotically.

. I don’t know if a robotic servicing mission has been considered ever since., But given that there’s, no true replacement for the Hubble Space Telescope, it would be nice if Congress could find a little bit of money for NASA or even the private sector to revisit the idea And keep Hubble going. Meanwhile I’d like to thank my Patreon supporters for helping to keep Launch Pad Astronomy, going. And I’d like to welcome my newest, patrons Jonah Alvaro, Bernal Gimeno and Zoran Laco., And if you’d like to join me on this journey. To this incredible universe of ours., Well, please make sure you subscribe and ring that notification bell so that you don’t miss out on any new videos. Until next time. Stay curious.

https://www.youtube.com/watch?v=1xdmcUAv5DQ