Post on 27-Jun-2020
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!