In August 2019, upon receiving data from the US Air Force, The European Space Agency (ESA) determined that one of their Earth observation satellites in orbit, Aeolus, was on a potential collision course with one of SpaceX’s Starlink satellites. After a few days, the collision probability had gone up, and ESA reached out to SpaceX to discuss their options. SpaceX told them that they had no intention to take any action. Therefore, for the first time ever in ESA history, they had to preemptively perform a collision avoidance manoeuvre.
Such collision risks with other satellites are expected to increase, as many companies, along with SpaceX rush to launch thousands of satellites in low earth orbit. This also causes issues for astronomers and astrophysicists trying to observe celestial objects. Two of the largest telecom companies in India (JIO and Airtel) have partnered with SpaceX Starlink to provide satellite internet in India, this is going to feed the demand for these constellations, which should raise eyebrows in the Indian astronomy and space community.
How does Starlink work?
Satellite constellation-based internet works via direct uplink and downlink with an antenna owned by the user which communicates with a satellite in the sky above it. There has to be a satellite to receive the signal in the field of view of the antenna for this to work. As users are spread all across the world, as are the data centres and servers, these satellites need to cover the globe. Starlink satellites orbit above Earth between 350 and 550 kms in various orbital shells. This range is called “low earth orbit” (LEO), and has been chosen to limit the communications delay due to distance.
More than 7000 Starlink satellites are currently in LEO. SpaceX’s Starlink is not the only company trying to do this. Amazon’s project Kuiper, European Oneweb and Chinese Qiafan are hot on their heels along with many others. By the end of the decade, close to 40,000 constellation satellites are expected to be in LEO to provide internet access. This significantly increases the risk of collisions and generation of space debris.
This image of Venus and the Pleiades shows the tracks of Starlink satellites. The reflective surfaces of the satellites, coupled with the fact that they are orbiting around Earth, mean that astronomical observations that require very long exposures capture “tracks” of the satellites in their images. Torsten Hansen/IAU OAE CC-BY 4.0
Space debris and satelite traffic
Space debris refers to any human-made object put into space which does not serve a purpose. These range from whole dead spacecrafts, satellites, broken parts, paint flakes, rocket booster fragments, etc.
It is possible to track large objects, however there are likely millions of untracked bodies which pose a threat to other spacecraft and satellites.
Almost every space launch generates some space debris and space agencies usually have plans to de-orbit larger spacecraft – by either combustion in the atmosphere or a safe fall into the ocean – to avoid certain orbits from being converted to junkyards.
Impacts and collisions can lead to “Kessler syndrome” which is a cascading event where debris from one collision impacts other satellites till the whole orbit becomes functionally useless, or even outright dangerous, as space debris travels at extremely high velocity of 10s of kilometers per second.
Near misses with Starlink have already happened, the above encounter with the ESA satellite being a major one. Reportedly, the Chinese Tiangong space station, which has people onboard, has also performed multiple manoeuvres to avoid collisions with Starlink satellites.
SpaceX has taken some proactive measures: their satellites have thrusters and an automated collision avoidance system. However, all debris is not tracked and impact from micrometeoroids, or the thousands of tiny rocks which fall into the earth’s atmosphere everyday, is completely random.
SpaceX’s stated reason for using LEO is that the debris generated by their satellites in will burn in the atmosphere due to atmospheric drag within 5 years; for threats due to kessler syndrome, that may be 5 years too many.
Debris poses a major threat to any space-based operations for all stakeholders, including ISRO and India’s budding space sector.
How satelite traffic disrupts space research
The second major concern is for astronomical science and broadly to the sky as our natural heritage. Each of these satellites reflect light, and appear as interference and trails in images taken of the sky, whether it they are from a phone camera or a sophisticated imaging system of an observatory telescope.
Observatories all around the world, including ones in India are being affected. There are some ways to mitigate the effect due to this interference, but some data loss is inevitable. The International Astronomical Union, the largest body of astronomers in the world, put out a statement expressing their concern many years ago.
Also read: Why Astronomers Are Up in Arms Against SpaceX’s Starlink Satellites
Even if mitigation is possible, it comes at a real cost. In a paper published in Nature Astronomy, it was suggested that for the upcoming Vera Rubin Observatory, the cost of mitigation would be $34.8 million for the full duration of the project.
For a field such as astronomy, which is severely underfunded, costs like this could be existential threats for certain projects, particularly in countries like India, with limited science and research budget.
Facilities in India will also be affected by the rapid growth in the number of constellation satellites, such as the Himalayan Chandra telescope, operated by the Indian Institute of Astrophysics; Devasthal Optical Telescope operated by ARIES, which is the largest reflecting telescope in Asia; the Mt. Abu observatory operated by the Physical Research Laboratory and many others. India is also a major partner in the development of one of the largest optical telescopes in the world, the Thirty Meter telescope, which will also have to mitigate these issues.
Quite like how optical telescopes are used by astronomers to observe celestial objects by studying the light they emit, radio astronomers observe and study celestial objects emitting light at radio frequencies.
The background image shows the double star Albireo in Cygnus and was taken on 26 December 2019. The lines are Starlink satellites moving across the field, generating noise. Photo: Rafael Schmall, NOIRlab.
CC-BY 4.0
Indian radio telescopes and Indian scientists excel in radio astronomy. The upgraded Giant Metrewave Radio Telescope (uGMRT) near Pune primarily observes the sky at low radio frequencies, it has contributed prolifically to studying cosmology, galaxies, and pulsars, among others. Other telescopes at the Gauribidanur Observatory, the SARAS-2 experiment of the Raman Research institute, etc also do exceptional science by observing the sky at low radio frequencies.
There are multiple studies which show that radio telescopes pick up radio emission from Starlink satellites, particularly at the radio frequencies at which the above telescopes operate.
A 2023 study showed that that unintended radio emission from Starlink can be detected between 110 and 188 Megahertz; these emissions will interfere with the observations of the uGMRT, whose observation band 2 ranges between 120 to 250 Megahertz.
It said that “The received power of transmissions from the detected Starlink satellites was often much higher than the brightest astronomical radio sources in the sky” for the Square Kilometer Array (SKA-low), a future radio observatory which will be the largest radio telescope ever constructed. India is significantly contributing to its development by being a member state of its consortium.
Planetary defence
The concerns are not just for astronomical science, whose impact may seem abstract at first glance, but also in mitigating certain global existential threats. Space agencies around the world monitor asteroids and bodies in the solar system which may impact the earth and pose a threat.
Such bodies could do irreparable damage, anywhere from leveling a city or cause an extinction level event for life on earth. Planetary defence against such events is something which the community takes very seriously and recent space missions such as DART have successfully shown that asteroid orbits can be deflected in case of a threat.
These bodies have to be tracked with telescopes which will be affected by the increasing noise due to these satellites, it becomes significantly harder to track and trace the path of these bodies as LEO becomes more crowded.
The need for greater scrutiny
Satellite based internet can be a useful technology, but rapid growth of bodies in LEO is a threat to all parties that want to be in orbit, or go beyond it, including ISRO’s missions. The agreements and plans to mitigate collisions have been between NASA and SpaceX – one agency and one company. Collision avoidance systems are neither standardised nor robust, and it is uncertain whether they ever will be, given the amount of debris in orbit. This does not even account for the many other companies racing to launch their own satellite constellations.
With more satellite constellations soon to be in orbit, there needs to be a global dialogue about the unintended consequences of LEO crowding, light pollution and space debris.
Indian Telecom corporations have been trying to partner with SpaceX for a long time, however the dialogue about the consequences of its effects on the broader Indian space sector and astronomers in India has not even begun. Scientists and engineers need to scrutinise this proliferation closely and be involved in negotiations and developing standards.
The outer space treaty, of which India is a signatory, forms the basis of space law. It underlines space being the province of all humanity, and not under any one sovereign. Its provisions also include a clause stating “states shall avoid harmful contamination of space and celestial bodies”.
We need to reflect on the consequences on the world when giant corporations started faring to “greater unknowns” in the 16th and 17th centuries, like the Dutch and the English East India companies, for resource extraction. The goals and ambitions of many private players in the 21st century space race are not unlike their 16th century brethren. Is space and the great beyond merely a venture to be conquered and colonised by a few corporations, or is it a common heritage, to be understood, studied and explored to benefit us all?
Neel Kolhe is a PhD Student in Astrophysics at the Paris Observatory; he acknowledges Dr. Rahul Dandekar and Dr. Pranavi A.R. for their insights on this piece.
