Written Evidence Submitted by SKA Observatory
The SKA Observatory (SKAO: https://www.skatelescope.org/), is an infrastructure to deploy and operate radio telescope facilities in Africa and Australia, ultimately creating the largest research infrastructure on the planet. Headquartered at Jodrell Bank in the UK, SKAO welcomes the opportunity to participate in the inquiry for the new UK Space Strategy and UK Satellite Infrastructure. As a host and one of the three principal financial contributors (the UK’s contribution alone to SKAO, over the next ten years, will be some €300M), the UK government is one of the primary stakeholders in the recently formed Inter-Governmental Organisation, SKAO, the first entirely dedicated to radio astronomy; as such, it is my view that the UK must consider the potential impact that space activities can have on research activities, ensuring that commercial or non-science imperatives operate sustainably alongside science being undertaken on the ground and in space. This submission considers the perspective for radio astronomy in the UK and globally.
Radio astronomy is the science dedicated to the study of radio emissions from space, from the Big Bang, the evolution of the cosmos, to the origins of life itself, it has revolutionized our understanding of the Universe. In addition to its fundamental contribution to human knowledge, the technical challenges, and demanding requirements needed to conduct modern radio astronomical observations continuously generate advancements applicable in other areas of benefit to society while also developing highly specialised personnel all around the world.
Radio waves emitted from celestial sources cover the entire radio spectrum, from 30 MHz up to 3000 GHz, in the form of broadband emission or narrowband spectral lines associated with natural processes occurring within them. Radio astronomy observes these extremely faint signals with a combination of high gain antennas (such as the Lovell Telescope in the UK or large antenna arrays like the soon-to-be-built SKA-Low in Australia with 131.000 antennas distributed over an area of about 13000 square kilometres, and its sister array SKA-Mid, which will consist of 197 15-m class dishes in South Africa) and very sensitive receivers which are usually cryogenically cooled.
Cosmic radio signals can be tens of millions of times fainter than a normal radio communication signal (a modern cell-phone located on the surface of the Moon would be seen from Earth as brighter than the strongest radio source in the sky), thus the presence of artificial signals in the same frequency or close to frequencies where a radio telescope is observing can completely blind it. With this in mind, the International Telecommunication Union (ITU) has reserved special radio spectrum bands for radio astronomy usage at the international level, where the presence of other radio communication signals is minimal and, in some cases, even prohibited. The advancement of techniques and technology in radio astronomy allows observations across much wider frequency ranges than the original protected ITU bands (established in the 1960s). Higher sensitivity and wider bandwidth receivers have facilitated new discoveries and research fields, but unfortunately this comes with the price of increased interference from artificial signals. To overcome this, future radio observatories such as the SKA are located in remote areas of the world protected by national Radio Quiet Zones. An RQZ is a geographic zone, defined by legislation, where the use of the radio signals is minimised in large portions of the spectrum to allow radio astronomical observations in bands otherwise not accessible.
RQZs such as the SKAO sites in Australia and South Africa, the NRQZ in West Virginia USA and the site of the FAST telescope in China -the largest non-steerable telescope on Earth- are not protected from interference from radio transmitters in space. Space platforms such as navigation satellites, telecommunication and broadcast satellites and weather radar satellites generate interference in radio astronomy receivers. Currently due to the limited number of sources, and the very narrow beams of the telescopes, it is possible to “point away” from a satellite or to know the infrequent times a satellite is passing through the beam of the telescope. Radio astronomy has developed techniques to largely mitigate these signals and conduct observations, but this situation is rapidly and dramatically changing.
The advent of the mega-constellations, where only one constellation alone will double the number of active satellites in Low Earth Orbit, poses a significant threat to radio astronomy worldwide. Observatories located in RQZs are going to see an increase in interference that, if left unmitigated, will have a seriously detrimental effect on the scientific output of modern radio telescopes such as the SKA. Future plans to saturate the low Earth orbits are especially worrying, and prospects of hundreds of thousands of satellites could damage our ability to study the cosmos from the surface of the Earth. To exacerbate this problem, a greater number of satellites increases the probability of a failure and could mean that a satellite with a faulty transmitter is left there polluting the spectrum for the time it takes to re-enter the atmosphere (could be several years depending on the altitude).
With these considerations, SKAO respectfully requests that the following recommendations be considered in your inquiry:
1- Consider the impact of space activities, especially, but not limited to, satellite constellations on radio astronomy observatories within and outside of the UK. This impact consideration should be included as a part of the requirements for new space missions.
2- Consider including a requirement that large constellations of satellites (>100 satellites) have active means to avoid pointing their beams towards radio telescopes on the ground.
3- Consider a requirement on the reliability of satellite platforms (from large satellites to nano-satellites) and the effect that a malfunctioning satellite can have on the radio spectrum.