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CHEOPS Enters the Game

The Egyptian monarch Khufu was the second pharaoh of the Fourth Dynasty, which dates him back to the earlier years of the Old Kingdom period around the 26th century BC. I mention this figure, about which all too little is known, because his name is a link between the great monuments of an early culture (Khufu seems to have commissioned the Great Pyramid of Giza) and present-day engineering. Imagine how wondrous the Great Pyramid would have been to the average passerby of the time, and then realize that Khufu’s Hellenized name was Cheops, a monicker reflected in the acronym of our recently launched CHEOPS exoplanet observatory.

I always enjoy untangling acronyms, some of which are more labored than others. Did you know, for example, that the name of the Japanese IKAROS solar sail is actually an acronym standing for Interplanetary Kite-craft Accelerated by Radiation Of the Sun? Then there’s OSIRIS-REx (also satisfyingly Egyptian), which weighs in as Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (!) We can include the doughty EPOXI: Extrasolar Planet Observation and Deep Impact Extended Investigation. Compared with all this, the ESA’s CHEOPS is pretty straightforward: CHaracterising ExOPlanet Satellite.

Launched from Kourou (French Guiana) aboard a Soyuz-Fregat booster at 08:54:20 UTC on December 18, the CHEOPS telemetry was picked up by the Troll Satellite Station in Queen Maud Land, Antarctica, verifying its survival of launch for controllers at INTA (another acronym: Instituto Nacional de Técnica Aeroespacial, which is Spain’s space agency) in Torrejón de Ardoz, near Madrid, and now we have a new exoplanet asset ready to undergo the testing that will precede full operations. The international nature of exoplanet research is again highlighted as we contrast what CHEOPS will do with the ongoing activities of TESS, NASA’s Transiting Exoplanet Survey Satellite. For CHEOPS is not seeking new planets but following up on earlier discoveries, measuring planet sizes against mass information to derive planetary density.

So we combine mass information from radial velocity observations with transit data to work out density, a well researched combination of our two most productive discovery methods. CHEOPS ups the game with instrumentation mentioned below. It’s a collaborative project, being developed as a Small, or S-class, mission in ESA’s science programme through partnership with Switzerland, and including significant contributions from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden, and the United Kingdom. A guest observer program offers 20 percent of the observing time to the astronomical community, with the other 80 percent being reserved for observations determined by the CHEOPS science team. It’s remarkable that the mission took only five years to go from project start to launch.

Günther Hasinger serves as the European Space Agency’s Director of Science:

“CHEOPS will take exoplanet science to a whole new level. After the discovery of thousands of planets, the quest can now turn to characterisation, investigating the physical and chemical properties of many exoplanets and really getting to know what they are made of and how they formed. CHEOPS will also pave the way for our future exoplanet missions, from the international James Webb Telescope to ESA’s very own PLATO and ARIEL satellites, keeping European science at the forefront of exoplanet research.”

Image: ESA’s Characterising Exoplanet Satellite, CHEOPS, lifts off from Europe’s Spaceport in Kourou, French Guiana. The Soyuz-Fregat launcher will also deliver the Italian space agency’s Cosmo-SkyMed Second Generation satellite, and three CubeSats – including ESA’s OPS-SAT – into space today. CHEOPS is ESA’s first mission dedicated to the study of extrasolar planets, or exoplanets. It will observe bright stars that are already known to host planets, measuring minuscule brightness changes due to the planet’s transit across the star’s disc. Credit: ESA – S. Corvaja.

Enough acronyms — we can unwrap PLATO and ARIEL as they once again appear in these pages down the road. What CHEOPS is all about, using transiting exoplanets as its fodder, is probing into the internal structure and composition of these worlds. Gaseous or rocky? Can we make inferences about possible atmospheres or oceans? Several hundred planets are under close investigation, all of them bright stars hosting known exoplanets in the size range between Earth and Neptune. ESA is saying that atmospheric observations including cloud cover may be possible for some, using phase curve methods that analyze reflected light as the planet orbits the host star.

Even moons or rings around some planets may be possible catches. As for new exoplanets, tight studies of the transits of known worlds may reveal by transit timing variations the existence of other worlds in the same system. CHEOPS may also snag a transit of planets previously known only through radial velocity study. We’ll be keeping an eye on CHEOPS and its high precision photometer, a 300 mm effective aperture telescope with CCD detector covering wavelengths between 330 and 1100 nm. Congratulations to the CHEOPS team on a successful launch and best wishes as operations commence in the observatory’s 700 km orbit.

{ 14 comments… add one }
  • Antonio December 20, 2019, 14:46
  • Michael C Fidler December 20, 2019, 19:39

    Paul, do you have any contacts with the ESA that can give us a run down the the initial period for testing and first light will be for Cheops? The early reports where saying something like a hundred to several hundred stars will be observed in the first 3.5 years, but have they released or do they plan to release a list of those stars? Is Cheops planning on an extended mission or will it not be capable of that? This mission only cost 50 million and 20 of them modified to a 50 centimeter mirror could do a lot of candidates since we will be hitting a 100,000 exoplanets candidates in the not too distant future. The current system is already overloaded and they could be built much cheaper by the dozen!

  • Robin Datta December 21, 2019, 1:13

    Cheops brings to mind something embedded there in my education from long ago:

    To quote:
    “The rat flea was collected in Egypt by Charles Rothschild along with Karl Jordan and described in 1903. He named it cheopis after the Cheops pyramids.”

  • Robin Datta December 21, 2019, 1:56

    It would be great if for some portion of that 20% of time offered to the astronomical community an large, SETI-type efforts be given first dibs. Although I would like to think that the first evidence could be relics (or post-biological systems) in the form of megastructures, transuranic elements, Matrioshka brains and such.

    • Antonio December 21, 2019, 16:45

      Mmm I’m not sure it would be a good instrument for SETI. It can only do phototometry, not spectroscopy.

  • Geoffrey Hillend December 21, 2019, 18:58

    Quote by Paul Gilster: ” using phase curve methods that analyze reflected light as the planet orbits the host star. ” to tell if it has oceans or cloudy etc. I assume that they look at the light variations of the planet as it moves around it’s orbit, e.g., in front of the star, and furthest distance or elongation from the star etc. I assume that they use the exoplanet transit spectroscopy method to accomplish this because the only way to differentiate what light comes from the star and what comes from the planet is when the planet goes behind the star when the planets light gets blocked and they subtract the star light from the star light plus planet light which reveals the planet light. There would have to be observations of a single star over a long period of time of accomplish this?

    No one has said much about using the transit spectroscopy method for the JWST, but direct imaging with a star shade would always be nice. I have always wondered what kind of propulsion system would a star shade have to use to move it in front of a star to block the light and keep it stable?

  • Ashley Baldwin December 22, 2019, 6:44

    The ESA mission ‘red book’ describes the mission operations shakedown period on launch as being driven by whether the scope can be directly inserted into orbit by its Soyuz launch vehicle ( where it is a secondary payload ) or would need to use its ADCS thrusters to finalise its circa 435 mile sun synchronous orbit. This would use some of its finite supply of hydrazine propellant and thus impact any follow on mission . The good news is that orbital insertion was spot on and a post insertion ground station check showed all instruments to be fully functional. All systems ‘go’ . So responsibility for the mission has been handed over from the launch provider to the science provider immediately . First RESULTs are expected in a few months which means science observations will commence nearly straight away. None of the drawn out delay of getting to the complex P2 orbit we saw with TESS.

    The ‘red book’ describes consumables for possible mission extensions of up to five years – reaction wheel failures and orbital debris not withstanding.

    Fingers crossed .

  • Harry R Ray December 24, 2019, 10:42

    THIS JUST IN: No Neptune(or larger)sized planets detected around either Alpha Centauri A or Alpha Centauri B with NEAR. For details, go to the Exoplanet.eu website and click on “Bibliography”. The paper states that these are just preliminary results, but made no mention as to whether or not sub neptunes may be in the data and can be pulled out of the existing data via further data reduction. My take: If they do tease something out, a planetary explanation would be at a very low confidence level.

  • Ashley Baldwin December 24, 2019, 19:49

    So NEAR…. yet so far.

    Well spotted.

    But don’t be despondent . Still plenty of room for optimism . NEAR was not a Doppler spectroscopy observation run where “negative” data can still indicate “signals” that don’t quite reach discovery level and which can be “binned” together with other observations to create a later “signal”.

    NEAR was direct imaging programme, combining the new deformable secondary mirror /Adaptive optics hardware on the VLT Unit telescope 4 ( UT4) in combination with a coronagraph, the N band ( 10 micron) NIR VISIR imager imported from UT3 and a few other temporary enhancements – all funded through Project Breakthrough .

    No planets Neptune sized or bigger means just exactly that . No Neptune sized planets. Good – we don’t want any such brute gravitational influences disrupting an already hair trigger and narrow stability binary gravitational environment .

    Ergo, smaller planets are NOT yet excluded.

    These results also show there were problems with the NEAR observation period which significantly reduced its sensitivity. As proposed it was already at the absolute limits possible for an 8m class telescope . Capable of a maximum contrast reduction of 1e7 in the N band with an inner working angle of lambda/D ( admittedly covering some but not all of the Alpha Centauri AB systems ) and a smaller discovery limit extending down to 1.9 Re planets . Half the size of the actual Neptune sized null results reported . And far from Earth sized .

    I had heard that the original observation run of 20 consecutive nights had been curtailed/disrupted , as had the hoped for 100 hours plus of actual observation time required . This is borne out by the considerably less sensitive discovery space reported .

    Good try but somewhat disappointing outcome given the time and effort involved. But still a successfully dry run of what is ostensibly a prototype of the potent METIS NIR instrument slated for the E-ELT.

    So still plenty of hope for Earth sized – or even Super Earth sized, planets in the habitable zones of both target star systems.

  • Harry R Ray January 7, 2020, 11:05

    YAY!!!!! JWST will STILL be able to detect oxygen in the atmospheres of the TRAPPIST-1 planets EVEN IF they are COMPLETELY COVERED by clouds. “Sensitive probing of exoplanetary oxygen via mid-infrared collisional absorbtion.” by Thomas J. Fauchez et al.

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