Who will keep the growing satellite sky dark and quiet?
memorandum of understanding
A formal document describing planned cooperation between organizations.
radio-frequency interference
Unwanted radio signals that disturb astronomical measurements.
IAU CPS
A centre that works to protect astronomy from satellite effects.
What happened
On October 7, 2026, the European Space Agency (ESA), Europe’s space agency, signed a memorandum of understanding with the International Astronomical Union’s Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (IAU CPS). The signing took place during the third day of IAC 2026. ESA says the agreement will bring the two groups into closer cooperation. They will look for solutions that support scientific discovery and the sustainable development of space activities. ESA’s announcement
What “dark and quiet” means
Dark and quiet describe two different kinds of interference. Satellites can reflect sunlight. That light may appear as bright points or trails in sky images. The IAU says optical and infrared effects from satellites are part of the dark-sky problem. Quiet-sky protection concerns radio-frequency interference from satellite constellations. It is not about making space silent. It is about limiting unwanted radio signals in astronomical measurements. IAU’s overview
Why it matters
The problem affects professional astronomy and ordinary stargazing. A bright trail can enter an image. Radio interference can enter a radio observation. In both cases, the unwanted signal can make the observation harder to interpret. The issue grows as the number of satellites in orbit grows.
This is also a coordination problem. Satellites are part of expanding space activity. Astronomers need a sky that does not add avoidable light or radio interference to their observations. ESA’s announcement places both goals in the same plan. It seeks ways to protect discovery while keeping space activities sustainable.
What is confirmed
The confirmed step is a cooperation agreement. ESA and IAU CPS will work more closely. Their stated task is to identify solutions. The announcement does not present a new satellite, a new observing instrument, or a completed technical standard. It also does not say that a specific operator must change its system.
What is still unknown
The announcement gives no detailed limits for brightness or radio emissions. It does not name a schedule for new guidance. It does not explain how satellite operators and observatories will share measurements. We also do not know which actions will be voluntary, technical, or tied to future policy. Those questions matter because a cooperation document is only the starting framework.
What to watch next
The next important news will be practical. Watch for shared observations, recommended operating practices, or tests of possible solutions. It will also be useful to see whether the work covers both visible and infrared light, and radio observations. The central question is simple: can satellite services and a usable night sky develop together? The ESA announcement starts that conversation. It does not yet give the final answer.
Sources: ESA’s announcement, IAU’s overview
ESA and IAU CPS want a darker, quieter sky
📰 Full story: Who will keep the growing satellite sky dark and quiet?
Satellites can affect stargazing and astronomy. Two space groups will look for solutions together.
radio interference
Extra radio signals that disturb an observation.
radio telescope
A telescope that studies the sky using radio signals.
IAU CPS
A centre that helps protect dark and quiet skies.
💡 The gist
- Satellite light can spoil pictures of the night sky.
- Satellite radio can disturb radio astronomy.
- ESA and IAU CPS will search for solutions together.
On October 7, 2026, the European Space Agency (ESA) made an announcement. ESA is Europe’s space agency. It signed a cooperation document with the International Astronomical Union (IAU). The IAU is an international group for astronomers. The partner centre is called IAU CPS. It works to protect dark and quiet skies from satellite effects.
The news covers two problems. First, satellites can reflect sunlight. They may look like bright dots or trails. Those marks can enter telescope images. They can also distract people who watch stars. Dark means more than turning off city lights. The IAU also includes optical and infrared effects from satellites.
Second, satellites can cause radio interference. Radio telescopes study the sky with radio signals. Extra signals can mix with their measurements. This is why quiet does not mean silent. It means fewer unwanted signals in observations.
The problem matters because satellites and astronomy share the sky above Earth. The number of satellites in orbit is growing. Astronomers need observations that are not spoiled by extra light. They also need radio measurements that are not disturbed. People who simply enjoy stargazing can notice the light problem too.
ESA and IAU CPS will work more closely. They will look for ways to support science. They will also support sustainable space activities. This is a cooperation plan. It is not a list of final fixes.
The announcement does not name a brightness limit. It does not give a timetable. It does not say what operators must change. Future updates may explain how the groups will measure the problem. They may also show how they will share solutions.
Next, watch for practical advice. Will the partners study real observations together? Will they suggest changes for satellite operators? Will their work cover light and radio problems? Those answers will show whether the agreement becomes action.
Sources: ESA’s announcement, IAU’s overview
Satellites and the dark, quiet sky
📰 Full story: Who will keep the growing satellite sky dark and quiet?
Some satellites can make stargazing harder.
artificial satellite
A machine people send to fly around Earth.
radio waves
Invisible waves that can carry signals.
IAU CPS
A group that helps protect the sky from satellites.
Satellites are machines flying around Earth. An artificial satellite can reflect sunlight. It may look bright at night. A bright trail can cross a star picture. That can make stargazing harder.
Satellites also send radio waves. A radio telescope studies the sky with radio waves. Unwanted signals can bother its work. Quiet means fewer unwanted radio signals.
The European Space Agency (ESA) is Europe’s space agency. The International Astronomical Union (IAU) is an astronomy group. Its IAU CPS helps protect the sky from satellites. ESA and IAU CPS signed a cooperation agreement. They will think of solutions together.
The message does not name the final solution. We do not know the schedule yet. We can watch for the next update.
Sources: ESA’s announcement, IAU’s overview