When you think of innovative new space launch concepts, you probably think of rockets like NASA's Space Launch System carrying telescopes or robotic explorers out into the sky. rockets are the main way of carrying things beyond Earth's gravity. An alternative and cheaper option might be from balloons.
The ancient Chinese military used balloons for signaling as far back as the 3rd century AD, and crewed balloon flight began in Europe in the 1780s. The Project Stargazer of the 1960s, for example, sent two men and a telescope into the air in a high-altitude balloon to observe the stars.
Recent developments in balloon technology from NASA mean balloons may once again prove their worth for cutting-edge astronomy projects, carrying high-tech telescopes up into the atmosphere from where they can observe the cosmos. We spoke to a researcher at the University of Toronto who is working on a new generation of balloon-based telescopes to learn how they are being used.
You need to understand why we send telescopes into space to begin with to understand why balloons have the potential to be used in telescope missions. If you want to look at distant objects, you need to account for the problems caused by the Earth's atmosphere.
Water in the atmosphere blurs images taken by ground-based telescopes. It's why telescopes are often placed in locations that are very dry and at high altitudes, like Mauna Kea in Hawai'i or the Atacama desert in Chile. Telescopes like Hubble are put into space to look at distant objects above the atmosphere.
If you want to put a telescope above the atmosphere, you should send it on a rocket. It's not easy to do and it's very expensive to fix any problems which occur and need hardware replacement, but it's a very reliable method for avoiding Earth.
For decades, balloons have been used in scientific research. The problem with using balloons for telescopes was light. Most scientific balloons are launched in Antarctica because the research hardware is powered by solar panels, which can only operate during daylight hours. It's not great for telescopes to be limited to the kind of research that can be done during the day.
For the first time, we will be able to do night work with the newly developed balloons from NASA.
There are many advantages to using balloons as a method of carrying telescopes. Launching a balloon is cheaper than a rocket. If you have to perform any maintenance on your telescope, it's relatively easy because you can bring it back to Earth and then relaunch it. When the Hubble telescope experienced hardware problems shortly after its launch in 1990, it was difficult to perform maintenance on it.
You can launch the system multiple times with ballooning. It doesn't have to work the first time because you're going to launch it for a single night to test it, then bring it down and reiterate. You don't need a very aggressive testing structure for orbital missions.
This testing drives up the price of missions. It is important to make sure that every piece of hardware works right out of the gate, that everything has multiple redundancies, and that all of them work with each other.
It is easier to change hardware design as you go along with ballooning. If you send a balloon high enough into the atmosphere, you can reduce the amount of water in the atmosphere.
Zero-pressure balloons work by releasing gas when the sun comes up. The balloon and gas contracts when the sun goes down. The new balloons keep the gas contained even when it expands. When the sun goes down, the balloon can stay in the air for months, because it isn't vented. The balloon is expected to last between 30 and 100 nights of operation, compared to the few days before.
Shabaan and his colleagues are using a new class of NASA balloon in their telescope project. SuperBIT is a project that will keep a telescope in the air and point it in the right direction. Their telescope can look out to the stars with an unprecedented level of detail if they can sense the minute movements of the balloon.
The issue of keeping the telescope pointed in one direction is crucial for accurate observations, and it is something that SuperBIT has a unique approach to. The outer frame, middle frame, and inner frame of the telescope move on different axes: yaw, pitch, and roll. Shaaban explained that if I experience some movement, I can change my mind by moving in any of the three directions.
It's hard to steer, but it's relatively easy to steer.
For really accurate readings, it needs to be even more stable. The mirror inside the telescope can move at a rapid rate of 50 motions per second. When light enters the telescope and appears to be shaking because of the small movements of the telescope, the mirror adjusts so that it arrives unshaken at the sensor. The data from the sensors on the telescope is used to calculate the movements of the mirror so it can be stable.
Those small movements are not made using thrusters, which would require fuel. Shaaban explained that they are made by taking advantage of the balloon's size, and that SuperBIT will sense the motions and use the power of the balloon to counteract them. The balloon is large enough to pour a cup of water into the ocean. The level of the ocean won't rise because there's no fuel to worry about.
A balloon that can lock onto a direction in the sky to observe with a high level of accuracy is the upshot of all of this. He explained that it will make sure that the telescope is not moving more than 20 millionths of a second.
You aim a telescope from a balloon. Is it possible to move the balloon itself? It can be difficult to get balloons exactly where you want them to be. You can use weather models to find winds that are blowing in a certain direction, and then adjust altitude to get to those currents. This allows you to move a balloon in a certain direction.
Steering becomes much harder when the load is very heavy. Most scientific applications don't require a balloon to be in a particular position on the Earth, it's more important to reach the altitude. The only concern for these kinds of missions is that the balloon doesn't go over populated areas for public safety.
You throw out a parachute when the balloon pops. It is like a skydiving mission.
The balloon heads up to an altitude of between 35 and 40 kilometers, in a region of the atmosphere called the stratosphere. That's above where planes fly but below where satellites like Starlink sit. It's high enough to see the curve of the planet, but not so high that you can see the entire Earth. It is not the most inviting environment, but it is not as cold as space. There's troublesome radiation there too, but it's not as bad as in orbit. It is space but different when it comes to the challenges we face.
If you want to recover a balloon load and reuse it, you wouldn't want your telescope to be dumped somewhere that is hard to access. The team chose to launch out of Palestine, Texas or Timmins, Ontario because they are both surrounded by large areas of land that are easy to recover the telescope from.
It can be difficult to land a balloon. The team added crash pads to the telescope to absorb some of the impact when testing the SuperBIT hardware. Sometimes they were lucky, and the telescope was relatively undamaged. Sometimes the hardware got banged up in the landing.
Even a seriously damaged telescope isn't the end of the world, as fixing it up is still cheaper than building a new telescope from scratch.
Testing space hardware to the degrees of accuracy needed when facing potentially unknown and extreme conditions is really, really expensive. There is a big advantage to any method which will allow you to launch missions and keep going as problems arise, instead of facing the impossible task of trying to predict and allow for any possible problem.
It is difficult to recreate space environments at a low cost.
SuperBIT has been through several test flights and is ready for science flights that were delayed by the Pandemic. The real focus of the project is on its successor, called GigaBIT.
Shaaban said that SuperBIT is a pathfinder experiment. The goal of the research is to create the highest resolution telescope that can be flown on a super-pressure balloon to meet the demand for high-resolution images at a much lower cost.
Because telescopes like Hubble are oversubscribed, many more projects want to use them than could possibly be given observing time. The team is building a bigger telescope to meet this need. The basic hardware will be the same as SuperBIT, but the telescope will be larger. To maintain the weight while adding a bigger telescope, GigaBIT will use carbon fiber instead of aluminum.
If a series of balloons could carry high-resolution telescopes like this one, and be regularly launched and landed as needed, it would be an aid to the world over.
Hubble has a significantly higher resolution than SuperBIT, but also a significantly smaller field of view. It is neither better nor worse. It has a lot of different scientific questions that it can address.
You might expect the advocates of balloon-based telescopes to promote them as superior to space-based telescopes like Hubble. He emphasized the potential for collaborations between ground-based, balloon-based, and space-based instruments.
Getting balloon-based telescopes off the ground means that more research can be done.