THE

MISSIONAndrea Fortier

on behalf of the CHEOPS Team Centre for Space and Habitability, University of Bern, Switzerland

Latin American Symposium on Small Satellites: Advanced Technologies and Distributed Systems 07. March 2017, Buenos Aires, Argentina

Overview

• Introduction to extrasolar planets • Mission Motivation, Objectives & Science Goals • CHEOPS Design • Mission status • Expected Performances • Summary

Introduction to extrasolar planets

• As of 6th March 2017, a total of 3,586 exoplanets in 2691 planetary systems (603 multiple planet systems) are listed in the Extrasolar Planets Encyclopaedia.

• The first confirmation of an exoplanet orbiting a main-sequence star was made in 1995, by M. Mayor & D. Queloz (U. of Geneva) when a giant planet was found in a four-day orbit around the nearby star 51 Pegasi. 51 Peg is a very bright, Sun-like star. 51 Peg b has a minimum mass about half of the mass of Jupiter.

What are exoplanets made of?

Introduction to extrasolar planets

What are exoplanets made of?

Introduction to extrasolar planets

gas giantsNeptune-like

planets

Earth-like planets

Why CHEOPS?

The transit technique

➨ radius of the planet

The radial velocity technique

➨ Mp sin(i)

Why CHEOPS?

The transit technique

➨ radius of the planet

Mp & Rp ➨ ρp

The CHEOPS mission

Milestone Timecall issued March, 2012

proposal due June, 2012

mission selection October, 2012

mission adoption February, 2014

launch End 2018

Nominal lifetime 3.5 years

ESA small mission requirements

• Science: top rated science in any area of space science

• Cost: cost to ESA not to exceed 50 M€ • Schedule: developed and launched within 4

years

Consortium MembersA mission of many challenges Small mission, large organisation!

SwitzerlandMission lead

Instrument lead Science operations centre

A mission of many challenges Small mission, large organisation!

PI: Willy Benz, U. Bern

C H E O P S Mission Consortium

GermanyFocal plane assembly & sensor electronics

ItalyTelescope

AustriaDigital processing unit, power converter & flight software

HungaryRadiators

BelgiumBaffle and Cover

SwitzerlandMission lead

Instrument lead Science operations centre Instrument

PI: Willy Benz, U. Bern

C H E O P S Mission Consortium

SwedenData flow simulator

UKQuick look

FranceData reduction pipeline

PortugalMission planning, archive, & data reduction pipeline

SpainMission operations centre

GermanyFocal plane assembly & sensor electronics

ItalyTelescope

AustriaDigital processing unit, power converter & flight software

HungaryRadiators

BelgiumBaffle and Cover

SwitzerlandMission lead

Instrument lead Science operations centre InstrumentGround Segment

Detect the transit of known super-Earths

Ground-based RV surveys HARPS, HARPS-N, HIRES, SOPHIE (ongoing) CARMENES, SPIRou, ESPRESSO (incoming)

Measure accurate light curves for Neptunes

Ground-based transit surveys NGTS (on going)

TESS (2017)

K2

20% open time (3.5-yr mission)

Observation strategy: Follow-up

What CHEOPS will do:➡ Perform 1st-step characterisation of super-earths & neptunes by measuring accurate radii & bulk densities for such planets orbiting bright stars

➡ Provide golden targets for future atmospheric characterisation by finding the planets most amenable to deep atmospheric studies

How CHEOPS will do it:➡ High-precision photometry (~ 20 ppm precision for bright stars)➡ Observing stars almost anywhere on the sky

CHEOPS science case

700 km

CHEOPS orbit

Sun

120°

OBS

ERVA

TIO

NS 35°

1 April

21 December

21 June

10 September

Orbit

Low (700 km) Earth Sun-synchronous orbit LTAN 6 am

✦ Earth occultation & stray light exclusion angle

✦ Sun exclusion angle

✦Moon exclusion angle

✦South Atlantic Anomaly

Low Earth(650-800 km) Sun-synchronous orbit LTAN 6 am

Observability constraints

Sky visibility

What is special about CHEOPS ?

CHEOPS is complementary to all other transit missions

CHEOPS is a photometric observatory looking at one object at a time

• it will measure highly accurate signals- 20 ppm accuracy over 6 hours for G-type stars with mV < 9

“super Earth”- 85 ppm accuracy over 3 hours for K-type stars with mV < 12

“Neptune characterisation"• it can point at any location over more than 50% of the sky

- can choose the best targets for transit search- can improve radius measurements- can confirm transiting planets on larger orbits- can search for additional planets

Design

CHEOPS design

Incident FluxIncident Flux

CHEOPS telescope

30 cm effective aperture optical bandpass 330-1100 nm, on-axis

carbon-fibre structure defocused PSF

payload mass 60 kg

CHEOPS: Spacecraft Accommodation

Primary structureSolar array

Fixed sunshield

Star Trackers Optical Heads

Secondary Structure

S/C contractor: ECE-CASA Total satellite weight: 280 kg

Total cost: ~ 110 M€

Telemetry: 1.2 Gbit/day (S-band) On-board data stacking

Measurement cadence: 1 min-1

Focal Plane

Frame-transfer CCD, e2v CCD47-20, AIMO

plate scale: 1 arcsec = 1 pixel

Stabilized @ -40 C to 10 mK

Observation principle

Frame-transfer CCD

1k×1k

Observation principle

200x200 subarray on-board stacking cadence 20–60 s-1

Observation principleCHEOPSim

Observation principle

24 pixels (24”)

•Jitter mitigation: • Pointing stability: jitter < 4” rms • PSF is purposely defocused • Pixel-to-pixel FF precision <0.1%

• Thermal stability: • Rotating field

• Triangular shape of the PSF

CHEOPS: Science Data

Exposure time per frame: 0.1 sec - 60 sec [0 sec - 10 min]Data download: on board co-addition (1 image per minute)

Mission status

Environmental tests

T/V chamber @U. Bern

Vibration tests

Shaking telescope @U. Bern

Shaking satellite @RUAG, Zurich

THE critical test!

@CASA, Madrid

CHEOPS performance

Performances

• Noises are estimated based on a mixture of • measurements

(e.g. RON, QE variability, pixel-to-pixel sensitivity) and • simulations

(jitter over CCD, shot noise, cosmic rays) • Predicted noise performance is calculated for three

reference cases:

Target Time-scale Name Predicted Noise

A G2 mag 6 6h “super Earth”: bright end 16.0 ppm < 20 ppm

B G2 mag 9 6h “super Earth”: faint end 18.6 ppm < 20ppm

C K2 mag 12 3h “Neptune characterisation” 79.5 ppm < 85 ppm

Summary

CHEOPS in the web: http://cheops.unibe.ch/ http://sci.esa.int/cosmic-vision/49469-cheops/

• CHEOPS is Europe’s next exoplanet mission (2018)

• CHEOPS is a follow-up machine, Knowing when to look at a star makes CHEOPS extremely efficient➡ Provides a first-step characterisation of low-mass exoplanets➡ Collects the golden targets for future in-depth characterisation ➡ Allows 20% open time for high-precision photometry science

CHEOPS Workshop + Open Time ConferenceSchloss Seggau / 24 – 28 July 2017

http://geco.oeaw.ac.at/links_CHEOPSsw17.html

Thank you!