Symposium Objectives

This symposium is planned as a dedicated space where astronomers, industry and other interested stakeholders can share the current status of their work with respect to large satellite constellations and their impact on astronomy and the night sky. Through presentations and panel discussions we expect to explore the current status of studies, observations and mitigations; also participants will be able to share their current or future lines of research in this area and discuss identified gaps that should be addressed.

Contributions in the following areas are encouraged (but not limited to): Policy, software, satellite tracking, space situational awareness, telescope mitigation measures, studies and observations, community engagement and awareness raising, spectrum management, others.

In addition to the next section on background information, you can visit the CPS website , which will inform you on the rapid growth in the space-based internet industry, as well as background on the effects on astronomy, mitigation strategies and the role in the UN Committee for the Peaceful Use of Outer Space.

Background information

The region of outer space near the Earth is changing. 65 years after the launch of the first artificial satellite, many thousands of satellites orbit our planet. Many more pieces of "space debris" or “space junk” have resulted from this activity. The space around our planet is growing ever more crowded, risking future catastrophes. This is the result of a new age in the use of outer space that began in 2019. Private commercial space companies began launching massive groups of satellites known as large "constellations". Although there is no precise definition of this term, it often refers to a group of satellites numbering from hundreds to tens of thousands. They are designed, launched and operated as a group for a common purpose, such as delivering broadband Internet access. Companies use large numbers of satellites in low orbits to ensure uniform coverage of the Earth and high network speed.

Credit: IAU CPS

Since the start of the large constellation era, the number of functional satellites has doubled to more than 5000. Space companies have publicly announced plans for the launch of up to 400000 satellites by 2030. More than one million debris fragments larger than 1 centimeter may already orbit the Earth. Hostile events, such as destructive antisatellite weapons tests, threaten to increase these numbers.

Credit: NASA (public domain)

Large constellations are altering the appearance of the night sky. Satellites and debris high above the Earth reflect sunlight to the night side of the planet, which makes them visible as moving points of light. These visible objects can disrupt navigational practices of traditional nighttime wayfinders. Swarms of satellites may interfere with the cultural and religious practices of some people. And they are an unwelcome intrusion for casual stargazers and all who love the tranquility of dark and quiet nights.


Astronomical telescopes now often record bright trails of light in photographs. Astronomers may lose data when satellite trails overwhelm the faint cosmic signals they collect. Large constellations and debris can raise the brightness of the night sky itself, making it difficult to see faint objects. Transmissions from satellites overload the sensitive detectors of radio telescopes. These effects are harming our ability to make new astronomical discoveries using telescopes on the ground. Not even space telescopes are immune to the problem. Satellite trails are evident in some Hubble Space Telescope images.

The life cycles of satellites also pose other environmental threats. Pollution from launches may add substances to the lower atmosphere related to climate change. Re-entering spacecraft may add alarming quantities of certain metals to the upper atmosphere. And there are potential impacts to wildlife and the ecology from large constellations. For example, adding many new and bright moving objects to the night sky could interfere with migratory species that use the stars to navigate.

Astronomers led the way in studying the effects of large constellations to understand the risks to the night sky. They have engaged directly with space companies, international bodies like the United Nations, and a diverse community of stakeholders. These efforts led to some spacecraft design modifications that yielded modest reductions in satellite brightness. At the same time, the pace of launches continues to increase. Risks to both the night sky and near-Earth space are great unless these resources are carefully managed. Yet there are few national or international laws or regulations that put meaningful limits on the acceptable amount of harm that satellites can cause to the night sky.

Credit: SpaceX

Astronomers are generally not opposed to satellites or large constellations of satellites. The potential benefits to humanity are great, but so are the associated concerns. Creative solutions and technological innovation are needed to confront and solve these problems.