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Satellite interference can overwhelm radio telescopes because the signals astronomers seek are exceptionally weak. The main pathways are satellite transmissions, unwanted emissions outside assigned channels, and unintended radio-frequency radiation from spacecraft electronics. A launch puts spacecraft into operation, but the sources cited here do not establish a general measured effect from rocket exhaust or launch acoustics themselves.
Why radio astronomy is vulnerable to satellite signals
Radio telescopes detect faint natural emissions, while communications satellites transmit signals powerful enough to serve users on Earth. The ITU Handbook on Radio Astronomy gives typical signal-to-noise ratios of −20 dB to −60 dB in radio-frequency and intermediate-frequency receiver stages. This describes the weak-signal environment, not a measured effect of any particular launch.
A remote observatory can avoid many sources of interference on the ground, but it cannot avoid satellites simply by being far from cities. Satellite signals may reach a telescope from above, and a dense satellite environment makes it harder to rely on scheduling alone, according to the ITU’s 2026 report.
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Intended transmissions
Communications transmissions are designed to carry usable power to receivers. A sufficiently strong signal entering a radio telescope can overload or saturate its receiver, obscuring the much weaker astronomical signal. Frequencies, power limits, and, in some cases, coordination obligations apply to these transmissions.
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Unwanted emissions beyond an assigned channel
Real transmitters can emit energy beyond their intended channel. Out-of-band emissions occur just outside the assigned channel; spurious emissions occur farther away and can include harmonics. Existing rules address unwanted emissions, although enforcement and possible refinement remain policy concerns.
Unintended radiation from spacecraft electronics
Spacecraft can also produce radio-frequency energy without using a communications transmitter. Potential sources include switch-mode power supplies, clocks and oscillators, digital backplanes, motor controllers, and solar-panel inverters. The ITU’s August 2026 article says this type of radiation is not explicitly addressed in most spectrum-management frameworks and reports no clear binding operator requirement specifically to prevent it. The article also describes reported LOFAR observations of unintended signals from second-generation Starlink satellites across 110 to 188 MHz; this is the ITU article’s account of those observations.
What a launch does—and what is established
A launch deploys spacecraft that may later add to the radio environment affecting observatories. The sources cited here document satellite-operation mechanisms and ways to mitigate them, but do not establish a general quantitative effect from launch exhaust, acoustic noise, or the launch vehicle itself on radio astronomy. That distinction matters: a satellite launch should not be described as disrupting every telescope, or as having a proven launch-plume effect on radio observations.
Ways to reduce interference
Coordinate spectrum use and observatory needs
International and national coordination can identify observatories, relevant frequency bands, and applicable limits. The International Astronomical Union’s Centre for the Protection of the Dark and Quiet Sky (CPS) provides a forum for international coordination, since satellite constellations and astronomy observations cross national borders. The IAU’s 2022 announcement described the need to turn cooperation among the astronomy community, industry, and policymakers into implementable actions.
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Share telescope data with satellite operators
Operational Data Sharing (ODS) gives satellite operators near-real-time information about a telescope’s sky position, observing frequency, and bandwidth. Operators can use it to adjust satellite activity during close passages. As ITU-R Report RA.2126-2 puts it, “The simple goal of ODS is to make the near real-time activity of the radio telescope (sky position, frequency, bandwidth) available to a satellite operator.” The report also envisions operators sharing back what actions they took.
ODS depends on timely information and an operator’s ability to respond. The ITU report says operators typically need at least 10 to 20 minutes to make mitigating changes, with some cases taking several hours. Those are operational observations in the report, not a guarantee for every satellite system. Telescope schedules can also change because of weather or new scientific opportunities.
Steer satellite beams away from telescope pointing
With boresight avoidance, a satellite can steer a phased-array beam away from a telescope’s pointing direction or briefly stop a downlink during a close passage. The ITU report documents a coordinated demonstration involving the Green Bank Telescope and an operator, and says parameters should be tested and refined using observatory measurements.
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This is a supplementary measure, not a complete barrier: sidelobes and scattered signals may still reach an observatory. The report cautions against treating boresight avoidance as sufficient for meeting the single-entry criterion.
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Protect the receiver and observatory
Observatories can reduce the effect of strong signals and local interference through equipment and facility choices:
- Bandpass, high-pass, or low-pass filters can suppress strong signals outside a desired range. Their insertion loss can raise system temperature near band edges, reducing sensitivity.
- Robust, linear receiver design can reduce concerns such as overload, aliasing, and intermodulation, with potential sensitivity trade-offs.
- Shielded cabinets and Faraday cages can limit locally generated radio-frequency interference.
- Remote observing and limits on consumer electronics can reduce interference from equipment near the telescope.
Use signal processing where appropriate
Multi-antenna arrays can apply spatial nulls or adaptive beamforming to reduce interference arriving from particular directions. Their effectiveness depends on the signal and observing scenario; they are not universal erasers and do not replace coordination or emission controls.
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The 2024 edition of the ITU Radio Regulations, Volume 3, includes Resolution 739-3. It calls on administrations to take reasonable steps toward specified unwanted-emission thresholds at radio astronomy stations and to consult when those thresholds cannot be met. Its scope is limited: it does not resolve unintended spacecraft radiation or provide universal protection from every form of satellite interference.
The ITU’s August 2026 article describes ongoing work toward practical electromagnetic-compatibility limits for unintended radiation from spacecraft, as well as WRC-27-related work on unwanted emissions. These are developing efforts, not completed universal limits.
Quick Recap
Sources and further reading
- ITU-R Report RA.2126-2 (March 2026)
- ITU: “Three kinds of satellite signal, three challenges for radio astronomy” (August 2026)
- IAU CPS launch announcement (10 June 2022)
- ITU Handbook on Radio Astronomy, vulnerability chapter
- ITU Radio Regulations, 2024 edition, Volume 3
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