Satellites rekindle the woes of interference for astronomers

This week marks the final launch of the European heavy rocket, Ariane 5. Launched on its final mission on July 5 from the European Space Base in Kourou, French Guiana, this rocket carries two communication satellites in an orbit set for a geostationary orbit, where the satellites will hover over a fixed point on Earth.

One satellite, Syracuse 4B, belongs to the French military, while the other, Heinrich-Hertz, is owned by the German Space Agency and is designed for experiments and research in communication technology.

Ariane 5, designed by European satellite launch company Arianespace, was developed in the 90s and first launched in 1996. Although it was originally designed to carry people, it was never ultimately designed to carry humans. now carry out any manned mission. Large rockets can carry payloads of more than ten tons to geostationary orbit and more than twenty tons to low-Earth orbit. Over a 27-year lifespan, 117 Ariane 5 rockets were launched. All of these are single use, with no recycled ingredients. Of these launches, 112 were completely successful, two failed, and three were marked as «partial failures».

The most recent partial failure occurred in 2018 when an incident caused the rocket to place a satellite in an incorrect orbit. However, satellite operators managed to adjust its orbit using stored fuel to continue the mission. Notable European rocket passengers include the James Webb Space Telescope, launched in December 2021, the Rosetta mission in 2004 – the first spacecraft to orbit an asteroid and most recently the JUICE mission, equipped with Israeli research equipment. equipment, sent to explore Jupiter and its moons.

The planned successor to this rocket is the Ariane 6, which has been in development for almost a decade. Slightly larger and more powerful than its predecessor, it runs on hydrogen and oxygen (with a solid fuel booster) and it’s also single-use – no parts recycled. Its first launch is scheduled for the end of this year and plans are in place for nearly 30 intended missions on the rocket.

The rapid deployment of large groups, incorporating dozens, hundreds, and even thousands of satellites, has increased dramatically over the years. Leading this trend is SpaceX, whose Starlink communications satellite network currently has more than 4,000 satellites, which are expected to exceed 10,000 in the coming years.

However, SpaceX is not alone, as many companies are developing and launching satellite beams for a variety of purposes, including telecommunications, navigation, weather monitoring and imaging. Reflections of light from these vast groups of satellites and their passage through the sky can interfere with astronomical observations, and their communications can disrupt radio telescopes. .

While these problems can be mitigated by coordinating orbits and frequencies with satellite operators, new research reveals inadvertent emission of radio waves from satellites, potentially interfere with the telescope. This concerns radiation emitted during normal operation of the satellite’s electronic equipment, even if not transmitted to the earth station.

The study, conducted at a radio telescope in the Netherlands, tracks radiation emitted from the constellation of Starlink satellites. In a paper in the scientific journal Astronomy & Astrophysics, researchers report that 47 of the 68 satellites tested emitted low-frequency radio waves, between 110 and 188 megahertz, that could disrupt radio telescope measurements. Some emissions were also detected between 150 and 153 megahertz, a frequency band reserved for radio telescopes regulated by the International Telecommunication Union. However, these rules only apply to terrestrial transmission facilities, so technically there is no violation here.

Co-author Benjamin Winkel from the Max Planck Institute for Radio Astronomy (MPIfR) in Germany said: «Our simulations show that the larger the constellation, the more important this effect becomes as radiation from all satellites combined”. “This makes us worry not only about the existing constellations, but even more about the planned ones – and also about the lack of clear regulation to protect the radio astronomy. from unwanted radiation.”

Decoding the history of the universe

Last week, the European Space Agency successfully launched the Euclid Space Telescope. The main mission of this telescope is to study the expansion of the universe and try to solve the mysteries of dark matter and dark energy. Equipped with a visible light camera and an infrared spectrometer, the telescope aims to measure the redshifts of billions of galaxies. This redshift measurement will provide insight into the speed at which these galaxies are moving away from us. Ultimately, the telescope is expected to survey about a third of the sky and collect data on galaxies located up to 10 billion light-years away.

The telescope’s scientific team includes more than 2,000 scientists from 300 research institutions across 16 countries – 13 from the European Union and the rest from the United States, Canada and Japan. Their mission will involve analyzing the vast amount of data transmitted by Euclid, in order to better understand the expansion of the universe and how it changes over time.

The telescope, which is about the size of a commercial vehicle and weighs about two tons, was launched on a SpaceX Falcon 9 rocket on July 1. From low Earth orbit, it is currently approaching point L2, a position where the balance of gravity from the Earth and the Sun allows it to remain with almost no energy loss. Here, it will maintain good companionship by joining other space telescopes, including the James Webb Telescope and the Gaia Telescope.

Named after the ancient Greek mathematician Euclid of Alexandria, hailed as the father of geometry, the Euclid telescope is expected to operate for about six years, with the hope it will help us. better understand the geometry of the universe and its composition.

As part of NASA’s Artemis program, the US Space Agency plans to land humans near the moon’s south pole. A key goal of this mission is to investigate the possibility of ice inside the craters permanently submerged in darkness, where sunlight cannot penetrate. Operating in such permanently obscured areas poses a significant challenge, as sunlight serves as the primary source of energy for charging electric vehicles and scientific equipment, for example. American company Maxar recently won a NASA grant to develop a system of mirrors that are placed in a lighted area and redirected sunlight to power solar panels located in the area. dark surface of the moon.

The system, called ‘Light Bender’, will consist of a lunar lander carrying two mirrors on a telescopic mast 20 meters high. Once the pole is deployed, a mirror captures sunlight and reflects it towards a second mirror, with the help of a robotic arm, which then directs the sunlight to an object. The distant target is located deep in the shaded area.

This innovative solution will allow astronauts to perform extended operations inside the crater during the lunar day, lasting about two Earth weeks. Maxar, which has extensive experience in developing robotic arms for space operations, including those used on Mars rovers, plans to introduce the functionality of the Light system. Bender on Earth for two years, before moving on to testing on the moon itself.