The Characterizing Exoplanets Satellite, officially known as CHaracterising ExOPlanets Satellite – or CHEOPS, is a joint European Space Agency and Swiss Space Office space telescope designed to study the formation and sizes of known transiting exoplanets.

Liftoff of the mission, which includes the first of the second generation of Cosmo-SkyMed satellites as well as three smaller CubeSats, took place from the Guiana Space Center on Wednesday, following a scrub during the countdown on Tuesday.

CHEOPS:

CHEOPS is the European Space Agency’s (ESA’s) first exoplanet study mission.

Part of ESA’s S-class (small class) missions, the telescope is a joint effort between ESA and Switzerland and contains “important contributions” from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden, and the United Kingdom of Great Britain and Northern Ireland.

Built on the Spanish SEOSAT platform, CHEOPS’s prime contractor is Airbus Defence and Space. The telescope was built in Spain.

Have you met #Cheops, our Characterising #Exoplanet Satellite?

🛰️☀️⚫️🟤🔴🟠🟡🟢🔵🟣 Check out our interactive #media kit to help you get ready for launch on 17 December! 🚀 👉https://t.co/d3TtkvplxZ pic.twitter.com/AYyv8ZIRSw — ESA_CHEOPS (@ESA_CHEOPS) December 10, 2019

The mission will be jointly managed by ESA and a consortium – with the Mission Operations Centre located in Torrejón de Ardoz, Spain, and the Science Operations Centre located at the University of Geneva, Switzerland.

In addition to CHEOPS’s primary mission, the telescope also serves a bridge to ESA’s next generation of exoplanet satellites (Plato and Ariel), both of which are set to launch in the 2020s.

Unlike its famous ESA and NASA predecessors – CoRoT (Convection, Rotation and planetary Transits), the Kepler Space Telescope, and the Transiting Exoplanet Survey Satellite (TESS) – CHEOPS’s primary purpose is not to find new exoplanets.

Rather, the joint European telescope is a paramount “follow-up” mission, with a primary purpose of studying known exoplanets to accurately measure their radii, mass, and density.

It will focus primarily on super-Earth to Neptune mass exoplanets in the 1 to 6 Earth radii size range.

By studying known exoplanets, CHEOPS’s controllers already know exactly when to point the telescope at a specific star to observe the transit of an exoplanet between the host star and CHEOPS – greatly improving efficiency.

CHEOPS will observe stars across the visible sky, and will return to specific stars to observe repeated transits of the same exoplanet in an effort to improve characterization accuracy and precision.

Moreover, observations by CHEOPS will help future space telescope missions – like the NASA/European/Canadian James Webb Space Telescope – identify the most suitable, and potentially habitable, exoplanets to target in the search for water and methane signatures in the exoplanets’ atmospheres.

All of this will combine to enable scientists to begin to piece together what exoplanets are made of, how they form, and how they evolve.

To this end, CHEOPS’s mission objectives are:

Use ultra-high precision photometry to measure accurate sizes of a large sample of Earth- to Neptune-sized planets, Measure light curves of hot Jupiters to see how energy is transported in planetary atmospheres, Combine CHEOPS size measurements with existing planet masses to constrain their composition and internal structures, and Identify prime targets to search for the fingerprints of key molecules in the planets’ atmospheres using future observatories on Earth and in space.

Unlike its famous predecessors, CHEOPS will not be sent into a sun-trailing orbit (Kepler) or a far-flung Earth orbit (TESS); it will instead operate from a 98.22° polar, dusk-dawn Sun-synchronous orbit 700 kilometers above Earth’s surface.

CHEOPS will be the second satellite to separate after launch.

Cosmo-SkyMed will separate first, after which the Fregat upper stage of the Soyuz launcher will perform two burns to raise its orbit and change its orbital inclination to those needed for CHEOPS.

The exoplanet satellite will then separate 2 hours 24 minutes 41 seconds after launch.

CHEOPS’s total launch mass is just 273 kg, and it is quite compact – with external dimensions of 1.5 x 1.5 x 1.5 meters arranged on a hexagonal SEOSAT platform from Spain.

While CHEOPS’s overall mass is 273 kg, the vast majority of that is fuel and the satellite bus it is built on; the actual optical telescope and scientific payload package totals just 58 kg.

The primary optical mirror for CHEOPS is 32 cm in diameter with an F/8 focal length capable of viewing the light spectrum in the 330 to 1100 nm range.

The communications systems and antennas on the telescope will allow for a 1.2 gigabit per day data downlink capability.

After separating from the Fregat upper stage of the Soyuz launcher, CHEOPS will undergo a series of activation and checkout operations before beginning its primary 3.5 year scientific mission.

During service, roughly 80% of the telescope’s time will be given to guaranteed observation time of known transiting exoplanets.

This amount of guaranteed observation time is suitable to achieve the mission’s primary goal of characterizing known exoplanets and improving our understanding of their mass, density, and composition.

Additionally, the guaranteed observation time will allow scientists to use the telescope to confirm the existence of known exoplanets that transit their parent stars when viewed from Earth that were not detected using the transit method but rather the radial-velocity method.

On Tuesday 17 December 08:54 GMT (09:54 CET) our #Cheops satellite will lift off on a mission to characterise #exoplanets 🚀🛰️✨ Are you ready to follow the launch? What do you know about this inspiring mission? Let's start with some key facts

⬇️➡️https://t.co/IBYn8uPnym pic.twitter.com/Prqd17qmmn — ESA Science (@esascience) December 16, 2019

Radial-velocity detection of exoplanets relies on minute and precise observations of how the gravitational force of unseen exoplanets tug and wobble their parent stars.

Moreover, while the primary mission objective is not to discover new exoplanets, part of the guaranteed observation time will involve searching known multi-exoplanetary systems for the potential discovery of as-yet-undetected exoplanets.

The remaining 20% of observation time on CHEOPS will be distributed among chosen research proposals submitted to ESA’s Guest Observers’ Program.

Examples of already approved Guest Observations on CHEOPS include:

aiming the telescope at the hot Jupiter planets HD 17156 b and kelt-22A b, warm Jupiter K2-139b, and multi-exoplanet systems GJ 9827 and K2-138,

observing of the exoplanet DS Tuc Ab (which was found by TESS), and

searching for exocomets around 5 Vulpeculae.

Cosmo-SkyMed:

The COnstellation of small Satellites for the Mediterranean basin Observation-SkyMed, or Cosmo-SkyMed, is a four-satellite Earth observation constellation from the Italian Space Agency.

It is the second generation of the system and will set a new performance standard for space-based radar observation systems in relation to precision, image quality, and the flexibility of user services.

A civil and military system, Cosmo-SkyMed is designed to address the requirements of both commercial and government customers, as well as the scientific community.

To this end, the satellites are equipped with Synthetic Aperture Radar to perform observations under any weather or light conditions.

They are manufactured by Thales Alenia Space.

Cosmo-SkyMed will be the first satellite deployed after launch.

It will be released 22 minutes 43 seconds after launch into a 699 km orbit inclined 97.81° to the equator.

It carries a liftoff mass of 2,205 kg, is built on the PRISMA satellite platform, carries S-band and X-band radar, and has an operational lifetime of seven years.