Satellites threaten astronomy, but there are opportunities too – 04/22/2023 – Science

Every night the stars in the sky compete with thousands of satellites. The number of space intruders grows steadily with the proliferation of satellite constellations; companies are planning to launch tens of thousands of orbiters to beam Internet and other communications signals back to Earth. These companies include SpaceX, which has already launched thousands of Starlink satellites, and Amazon, which intends to launch its Project Kuiper constellation later this year.

For astronomers who study the universe from the surface of our world, it’s a problem that keeps getting worse.

“It’s a hot topic,” commented astronomer Eric Burns of Louisiana State University. “We are talking about satellites in such large numbers that they are limiting the sensitivity of Earth-based telescopes.”

Many astronomers are highly critical of the effects that satellite constellations have and will have on their studies. But Burns and other scientists are thinking about how to use these orbital lemons to create cosmic lemonade. They ask: what if all these rogue satellites could help advance the field of astronomy by expanding terrestrial access to satellite signals?

What these astronomers see is the potential for a new kind of telescope that satellite megaconstellations can make possible. In a proposal that Burns and his colleagues intend to present and share with private companies that are building satellite constellations, they hope that thousands of gamma-ray detectors could go into space hitchhiking on satellites. Each detector individually would be weak. But operating together within a megaconstellation of many thousands of satellites, the power of such a system could rival Swift and Fermi, two gamma-ray observatories in space run by NASA.

The impact would be significant. Gamma-ray bursts are the hallmark of the universe’s most catastrophic events since the Big Bang. Further research into the phenomenon could help provide answers to today’s biggest questions, such as what makes neutron stars’ colors different or how the behavior of dark energy can reveal the shape of the universe.

“These are the most important sets of questions you can ask in astronomy,” Burns said. “We’ll be able to treat the thousands of gamma-ray detectors as a single, coherent, extremely powerful telescope that will look everywhere in the universe and be more sensitive than anything done so far.”

The idea is not without precedent. In 2011, Iridium Communications worked with scientists to hitchhike research instruments into space. About 30 Iridium satellites — which typically transmit voice and data communications back to Earth — also house dosimeters that measure radiation in low Earth orbit as part of the Reach program, a collaboration between the US Air Force and scientists.

And all of Iridium’s 60-plus satellites carry magnetometers for the Ampere program, run by the Johns Hopkins Laboratory for Applied Physics, which studies how energy enters Earth’s ionosphere from its magnetosphere.

Alexa Halford, associate laboratory director at NASA’s Goddard Space Flight Center, says iridium readings are an important source of radiation data. Her work reveals the connection between Earth’s magnetosphere and atmosphere and how the two work together to protect Earth from showers of strong space radiation.

Halford said the ways in which megaconstellations of satellites interfere with telescopes on Earth’s surface need to be studied further.

“Earth-based astronomy is incredibly important, and we need to act responsibly,” she said.

On the other hand, she sees enormous potential in putting scientific instruments on more satellites.

“More data can give us a more complete picture,” said Halford. “I would have a hard time saying no to that.”

SpaceX is already sharing some data with scientists, in an arrangement that could benefit both parties.

Tzu-Wei Fang, a scientist at the US Oceanic and Atmospheric Administration who specializes in forecasting weather conditions in space, began collaborating with SpaceX after a disastrous launch in February 2022. SpaceX watched as 38 of its 49 Starlink satellites that had just been sent into space burst into flames.

The “autopsy” performed by Fang documented how a mild geomagnetic storm had raised the air density at altitudes at which low Earth orbits occur. So, instead of going into orbit, the Starlink satellites collided with hot, dense air and broke up.

“No one is able to do low-altitude Earth orbital trawlers very well right now because we don’t have the right satellites,” she said.

After that incident, SpaceX agreed to share the positioning and velocity data of its approximately 4,000 Starlink satellites for a year, giving Fang and his colleagues the opportunity to study the type of orbital drag that destroyed the satellites. That could lead to better space weather forecasts, giving satellites more time to react to an increase in air density, rising to a safer orbital altitude, “which ultimately benefits everyone,” Fang said.

Obtaining scientifically useful data from satellite constellations poses technical hurdles. Satellites in low Earth orbit travel very fast, completing a full orbital circuit in 90 minutes. Thus, combining data from a constellation of many satellites is not easy.

In order for scientific equipment to be able to hitch a ride in orbit, there are strict limitations that must be respected. Communications satellites in low Earth orbit, such as SpaceX’s Starlink, have a short lifespan — about five years — so the detectors would have to be inexpensive. By way of comparison, the Hubble Space Telescope cost about $16 billion in today’s prices, but is expected to last around 40 years.

Any additions couldn’t just be added at the last minute. Satellite engineers would have to modify their designs, with upgrades such as power supplies and larger data links, to accommodate the new payloads.

The need to negotiate one-on-one with hesitant companies like SpaceX has frustrated astronomers to this day. Burns thinks it may be time to ask for government oversight to ensure that satellite megaconstellations do as little harm to science as possible.

With greater participation, Burns hopes that scientists and satellite manufacturers will learn to work together. “I really think this idea of ​​putting scientific instruments in the megaconstellations themselves would benefit both parties,” he said. “If companies are open to the idea, it will be an even better solution.”