Lessons from Your Friendly Neighborhood Astronomer
The Hubble Space Telescope: 1990–2021?
NASA scientists are still working to save the legendary telescope
This is the second installment (and first science article!) in our new series, covering fundamental topics in astronomy and connecting them to recent discoveries and newsworthy events. You can find the cornerstone post here.
Launched in 1990, the Hubble Space Telescope has been shaping the field of astronomy for over 30 years. Unfortunately, this also means that it’s quite an old piece of equipment, with the main payload computer having been built in the 1980s.
The Hubble Space Telescope (also known as HST) was the first large observatory in orbit around Earth — a momentous milestone in the history of astronomy. The idea of doing astronomy from beyond Earth’s atmosphere is a relatively new idea, pioneered by astronomer Nancy Grace Roman (known as the “Mother of Hubble”) in NASA’s early days in the 1960s.
Why Space Telescopes?
Considering what an engineering challenge it is, why would we want to put telescopes in space? There are two main reasons. First, there are some wavelengths of light that we simply cannot see from the ground. For example, Earth’s atmosphere blocks out ultraviolet light, which is a good thing for us and all other life — but these higher energy light rays can also tell us some very interesting things about our Sun, how galaxies form, and more. Secondly, Earth’s atmosphere is like looking through a dirty car window. Our turbulent, ever changing atmosphere makes it hard to take a crisp picture of outer space, preventing us from seeing fine details in far away galaxies and other objects. By going to space with our telescopes, we can see interesting wavelengths of light we cannot see from the ground, and we get clearer images to see details.
These two motivating factors led Roman and her team at NASA to develop a series of satellites known as the “Orbiting Solar Observatories” and the “Orbiting Astronomical Observatories” — telescopes that paved the way for the future HST. In the 1970s, right before her retirement, Roman led a planning committee to design the foundations of HST, which finally launched almost 20 years later after decades of engineering and planning.
A good rule of thumb for astronomy is: if you build a better telescope, you will find a treasure trove of unexpected new discoveries. Hubble provided astronomers with exactly that, a revolution in almost every subfield of astronomy, from small planets to the largest structures in the universe. Hubble also took many of the iconic images of outer space we know and love today. Part of what makes Hubble unique is that it can “see” in multiple wavelengths — high energy ultraviolet, the visible light our eyes can see, and lower energy infrared.
A Sampling of Hubble’s Discoveries
Let’s look at a few of HST’s many discoveries to get an idea of just how influential this telescope is. Spiral galaxies, seen merging together, provide clues as to how bigger, elliptical galaxies form.
Hubble has taught us about how planets form, observing dust swirling around a star to make planets. It has also discovered many new asteroids and dwarf planets in our solar system and even planets around other stars (known as exoplanets).
HST has even contributed to solving one of the biggest puzzles in astronomy — what’s going on with dark matter and dark energy? Using a mechanism called gravitational lensing, data from Hubble helped trace how the mysterious dark matter is distributed throughout galaxies. Other data from Hubble also showed that the universe is expanding faster and faster, due to dark energy.
Its storied history hasn’t been without some hiccups, though. When first launched, Hubble’s mirror was slightly flawed — a problem that seriously blurred its vision. Scientists had to design a sort of “corrective lens” for Hubble’s bad vision, which was installed in 1993 thanks to astronauts on the Space Shuttle. This is one of the huge benefits of Hubble’s design and location in space — it’s within reach for crewed missions to repair it.
Hubble has been repaired and upgraded multiple times since then. Some parts were replaced and new capabilities added in 1997, and an urgent failure of one of the steering systems prompted another repair mission in 1999. A 2002 mission added a new advanced camera, and the final shuttle repair mission in 2009 installed and repaired many systems to prolong Hubble’s operations. Since then, it’s been up in orbit for over a decade with no repairs, chugging along doing science.
An Uncertain Fate
Now, the fate of the Hubble Space Telescope is up in the air (again), and in the hands of NASA’s engineers. On June 13th, the telescope’s main computer stopped receiving a “keep alive” signal from the science instrument computers. This signal is a sort of “handshake” between the two systems, indicating that all is well, so losing the signal is a red flag for a problem going on.
Thankfully, spacecraft are designed with failsafes to make sure no catastrophic damage happens before engineers have some time to figure things out. When this signal didn’t come across, the main computer put all the systems into a “safe mode” to halt operations. Scientists at Goddard Space Flight Center took note of the problem, restarted the computer, and rebooted the system. Then it happened all over again.
Scientists are now trying to restore functionality to the computer system, which appears to have an old, broken memory module causing the problem. Again, spacecraft are designed with redundancy, so there are two other backup memory modules that could be used. The team tried to switch to these backups, but have not had any luck so far.
Besides the memory modules, there are multiple other pieces of hardware in the system, and scientists need to figure out which one is causing the problem. They are now reviewing procedures and completing a simulation of the work they need to do, in order to prepare for actually turning on some of the sensitive backup hardware.
The efforts are still continuing, hoping to fix this critically important, historic telescope. Fingers crossed Hubble has many years of science left!
You can get up to date news on Hubble’s status here on NASA’s Hubble News.