cheops - Leiden Observatory

An S‐class mission 

New class: XLC mission ≤ 50 M€ 

René Liseau - Onsala Space Observatory - Sweden

An S‐class mission 

with 

launch 2017

it all began – in Sweden… an SNSB 2011 initiative 

1. 

2. 

3. 

4. 

5. 

PressPressmeddelanden 

Fem innovativa satellitförslag går till final 

I höstas efterlyste Rymdstyrelsen förslag på nya innovativa svenska satellitprojekt till låg kostnad, under 40 miljoner kronor. Nu har fem av 

inlämnade förslagen valts ut och går vidare till tekniska förstudier. 

Totalt skickades tolv förslag från flera olika forskningsområden in till Rymdstyrelsen. Efter 

utvärdering av en internationell expertgrupp har Rymdstyrelsen idag beslutat att fem av 

förslagen får gå vidare till teknisk utvärdering. Ett mål för Rymdstyrelsens utlysning är att 

ytterligare stimulera nya idéer inom rymdteknik och forskning t.ex. miniatyrisering och 

kostnadseffektiva byggnadssätt. 

– Vi vill visa att den typ av ny teknik som Rymdstyrelsen stöttat kan användas för att förändra 

sättet man bygger rymdprojekt på och visa att det går att leverera utmärkta forskningsresultat 

för mycket mindre pengar, säger Johan Köhler, forskningshandläggare och ansvarig för 

projektet vid Rymdstyrelsen. 

Följande förslag har av Rymdstyrelsen tagit ut till final: 

CHEOPS – (CHaracterizing ExOPlanet Satellite) mäter egenskaper hos planeter runt andra 

stjärnor. Ansvarig: René Liseau, Chalmers. 

Alfvén – (Explorer of small scale structure in the aurora) utforskar av fina detaljer i norrsken. 

Ansvarig: Hans Nilsson, IRF, Kiruna. 

METAL – (Microspacecraft interplanetary mission to a magnetized metallic M-class 

asteroid) besöker för första gången en metallisk asteroid. Ansvarig: Jan-Erik Wahlund, IRF, 

Uppsala. 

Tor – studerar växelverkan mellan solvind och jordens magnetosfär bl.a. turbulenta 

fenomen. Ansvarig: Andris Vaivads, IRF, Uppsala. 

MATS – (Mesospheric waves from airglow transient signatures) studerar vågrörelser i högre 

atmosfärslager som mäts in från ljussken alstrade på dessa höjder. Ansvarig: Jörg Gumbel, 

MISU. 

Nästa steg i processen är att Rymdstyrelsen låter svensk industri utföra tekniska förstudier av

Content 59 Biesbroek, Robin 

robin.biesbroek esa.int 

ESA 

S-LUNA 

11-October-2012 10:06:36 

S-class mission Letters of Intent 

61 Tavani, Marco 

GAMMA-LIGHT 

pi.agile iasf-roma.inaf.it 

In response to the "Call for a Small mission opportunity in ESA's Science Programme for 

INAF 

a launch in 2017", issued on 9 March 2012, the following Letters of Intent (LOI) have 

been 62 received: 

Foing, Bernard 

SMART+ 

b.h.foing vu.nl 

Ref. Contact Vrije Universiteit name, Amsterdam & ESTEC Title of LOI 

65 

Email, 

Anagnostopoulos, Georgios 

Institution 

ganagno ee.duth.gr 

Validation of the Lithosphere-Atmosphere- 

Ionosphere-Magnetosphere Coupling Concept 

2 Sutton, Demokritos James University of Thrace 

ESA Associated Small Mission with great Letter (M>4.5) of Intent Earthquakes - by 

jrfsutton virginmedia.com 

Immunogenetics 

using low orbit satellite observations 

66 

Sutton 

Drinis, John 

ESA S-Class Mission 

5 Khalesi, ydrinis algosystems.gr 

Mandali 

mandali Algosystems uchusencompany.com 

MAGES - Magnetospheric Earth Swarm 

68 

Uchusen Company Ltd 

Rigatos, Gerasimos 

ESA S-Class Mission 

6 Rudawy, grigat isi.gr Pawel 

Advanced Solar-Terrestrial European X-ray 

rudawy Industrial astro.uni.wroc.pl 

Systems Institute 

spectrophotometer: ASTEX 

69 

Space Research Centre Polish Academy of 

Bombardelli, Claudio 

Sciences 

claudio.bombardelli upm.es 

S-class mission to a nearby asteroid 

7 Jansen, Technical Frank University of Madrid 

SmallCostSat 

70 

frank.jansen dlr.de 

Ursin, Rupert 

DLR Institute of Space Systems 

rupert.ursin univie.ac.at 

Space-QUEST 

8 De IQOQI Ridder, Joris 

PlanetVision: Characterizing Planetary Systems 

71 

joris ster.kuleuven.ac.be 

Malbet, Fabien 

KU Leuven 

Fabien.Malbet obs.ujf-grenoble.fr 

micro-NEAT: a high precision astrometry mission 

to identify the high-mass planets around nearby 

9 Baan, IPAG Willem 

SURO-LC: stars The Space Based Ultra-Long 

72 

baan astron.nl 

Sarris, Theodoros 

Netherlands Institute for Radio 

tsarris athena-spu.gr 

Astronomy 

ATHENA-SPU 

Wavelength Radio Observatory 

Low-Flying Spacecraft 'Daedalus' 

73 Ciufolini, Lgnazio 

ignazio.ciufolini unisalento.it 

Università del Salento 

74 Baratoux, David 

david.baratoux irap.omp.eu 

Université de Toulouse, UPS-OMP, IRAP 

Testing General Relativity with laser ranged 

satellites 

Space-based observatory for optical monitoring 

of meteoroids colliding with the Earth 

74 LoIs 43 proposals & CHEOPS made it to

implemented for the first small mission opportunity in 2017 (“S1”). 

the top ten selected by the advisory bodies 

The 10 proposals that were submitted to the Advisory Structure for the evaluation were: 

1. AXIOM-C (X-ray imaging of the magnetosphere – cusps) 

2. CHEOPS (Exo-planetary transits) 

3. LARES-2 (Fundamental physics and general relativity testing) 

4. MASE (Magnetic activity of stars and exoplanets) 

5. NITRO (Composition measurement in the inner magnetosphere and auroral region) 

6. PlaVi (Exo-planetary transits and asteroseismology) 

7. SIRIUS (Ultraviolet spectroscopy of stars and insterstellar medium) 

8. TOR (Energy dissipation in solar wind turbulence) 

9. SIGMA (Measurements of the solar corona magnetic field) 

10. XIPE (X-ray imaging polarimetry) 

At their extraordinary meeting shown on here September in alphabetical 20 the SSAC, order 

having carefully considered t 

advice received from the Working Groups, unanimously recommended the CHEOPS missi 

proposal for implementation as the first Small Mission, S1. 

Following the advice of the SSAC, the Director of Science and Robotic Exploration 

herewith proposing to select the CHEOPS mission as the first Small Mission for launch 

2017. Should the SPC approve the proposal, the Executive intends to immediately start t


the top ten selected by the advisory bodies 












At their extraordinary meeting on September 20 the SSAC, having carefully considered t 

advice October received 19, from 2013 the Working Groups, unanimously recommended the CHEOPS missi 


SPC decision for S1 = 

Selected as No. 1 
















At their extraordinary meeting on September 20 the SSAC, having carefully considered t 

advice October received 19, from 2013 the Working Groups, unanimously recommended the CHEOPS missi 


SPC decision for S1 = CHEOPS 



h#p://www.esa.int/esaCP/SEMXFG4S18H_index_0.html 


Austria 

Belgium 

Switzerland 

France 

Italy 

Sweden 

United Kingdom 

CHaracterizingExOPlanet Satellite Proposal #12 for ESA S-Mission Call 

!"#$%&$'()$%*+,' 

Confoederatio Helvetica – led mission… 

Mission Coordinator: 

Prof. Willy Benz 

Physics Institute 

Center for Space and Habitability 

Sidlertrasse 5 

3012 Bern 

Switzerland 

e-mail: willy.benz@space.unibe.ch 

Proposing Team Members: 

Mission Project Manager: 

Dr. Christopher Broeg 



Sidlerstrasse 5 

3012 Bern 

Switzerland 

e-mail: christopher.broeg@space.unibe.ch 

Country Institute Short Name 

A Institut für Weltraumforschung, Graz, Austria IWF Wolfgang Baumjohann 

B Centre Spatial de Liège CSL Etienne Renotte 

B University of Liège ULg Michaël Gillion 

CH Swiss Space Center SSC-EPFL Anton Ivanov 

CH ETH Zürich ETHZ Michael Meyer 

CH Universität Bern UBE Nicolas Thomas 

CH Observatory of the University of Geneva UGE Didier Queloz 

F Laboratoire d'astrophysique de Marseille LAM Magali Deleuil 

I Osservatorio Astronomico di Padova - INAF INAF-OAPD Roberto Ragazzoni 

I Osservatorio Astrofisico di Catania – INAF INAF-OACT Isabella Pagano 

I Università di Padova UPD Giampaolo Piotto 

S Onsala Space Observatory, Chalmers Univ. of OSO Rene Liseau 

Technology 

S Stockholm University, Stockholm UST Göran Oloffson 

UK University of Warwick UWW Don Pollacco 

Associated Scientists and Engineers: 

Austria: Manuel Güdel (UniW), Helmut Lammer (IWF), Manfred Steller (IWF), 

Belgium: Brice-Olivier Demory (MIT/ULg) 

France: François Bouchy (IAP/OHP), Guillaume Hébrard (IAP/OHP), Patrick Levacher (LAM), 

Claire Moutou (LAM), 

Italy: Demetrio Magrin (INAF-OAPD), Jacopo Farinato (INAF-OAPD), Antonino F. Lanza (INAF- 

OACT), Giuseppina Micela (INAF-OAPA), Emilio Molinari (INAF-FGG), Valerio Nascimbeni 

(UPD), Salvatore Scuderi (INAF-OACT), Alessandro Sozzetti (INAF-OATO) 

Sweden: Alexis Brandeker (UST), David Hobbs, Anders Johansen (both Lund Observatory), Kay 

Justtanont (OSO) 

Switzerland: Yann Alibert (UBE), Roi Alonso (IAC Spain), Mathias Beck (UGE), Federico Belloni 

(SSC-EPFL), Bruno Chazelas (UGE), Piers Christiansen (UBE), Andrea Fortier (UBE), Kevin Heng 

(ETHZ), Luzius Kronig (SSC-EPFL), Daniele Piazza (UBE), Sasha Quanz (ETHZ), Udo Wehmeier 

(ETHZ), Francois Wildi (UGE), 

United Kingdom: Andrew Cameron (St-Andrew UK)

So, what is CHEOPS ?

Winn 2009

elies completely 

on components 

with flight heritage

Targets: known to harbour planets 

nearby bright stars 

spectroscopy e.g. JWST, ECHO 

known ephemerids 

O 2 C residuals (m s ) 1.20 

Reduced x 2 value 1.51 

BJD, barycentric Julian date; O 2 C, observed minus calculated. 

Fig. 4b we show that the 3.236-d signal conserves its phase for each 

observational year, which is expected for a planetary signal. 

An important piece of information about the inner composition of 

an exoplanet is obtained when the planet is transiting its parent star, 

allowing its radius to be measured. Combined with the real mass 

estimate, the radius leads to the average density of the planet. In the 

present case, given a stellar radius 36 of 0.863 times the solar radius and 

assuming the radius of the planet is that of the Earth, the planet transit 

probability is estimated at 10%, with a transit depth of 10 24 . The 

known distance (π HIPPARCOS/GAIA) 

a Centauri B. 

known radius/mass (θ VLT-I/a-seismology) 

known spectrum (Teff , [Fe/H], log g) 

detection of a planet transit, only possible from space, would allow 

us to confirm the expected rocky nature of the detected planet around 

The r.m.s. radial velocity induced by the stellar rotational activity 

amounts to 1.5 m s 21 on average. The detection of the tiny planetary 

signal, with a semi-amplitude K 5 0.51 m s 21 , thus demonstrates that 

stellar activity is not necessarily a definitive limitation to the detection 

of small-mass planets. Using an optimized observational strategy and 

the present knowledge about activity-induced radial-velocity effects, 

it is possible to model precisely and mitigate activity signals, and 

therefore improve considerably the planet detection limits. 

With a separation from its parent star of only 0.04 AU, the planet is 

orbiting very close to a Centauri B compared to the location of the 

habitable zone. However, the observed radial-velocity semi-amplitude 

is equivalent to that induced by a planet of minimum mass four 

times that of Earth in the habitable zone of the star (P 5 200 d; ref. 37). 

RV (m s –1 ) 

2.0 

1.5 

1.0 

0.5 

0.0 

–0.5 

–1.0 

–1.5 

–2.0 

0.0 0.2 0.4 0.6 0.8 1.0 

Phase 

Figure 5 | Phase-folded radial-velocity curve with a period of 3.2357 d. 

Green dots, radial a = 9 Rvelocities B 

after correction of the stellar, binary and 

coordinates effects. Red dots, the same radial velocities binned in phase, with a 

niqu 

tim 

Rec 

tion 

sho 

the 

Rece 

Pub 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

11. 

12. 

13. 

14. 

15. 

16. 

17. 

18. 

19. 

20. 

21. 

22. 

23.

,)&()0'/+&1) 

ence of the event, and the detailed shape of the transit light curve 

e eclipse and the ratio of the planetary radius to that of the star, (2) the 

ensity of the star 

law from the 

transit). These 

the effective 

osphere and an 

rieving the mass 

and finally the 

he planet. (Mazeh 

The precision of 

directly affected 

stellar parameters 

ht curve during a 

eraged over the 

the transit signalof 

a hot Neptune, 

y 3 hours, for a 

urs. In both cases 

10 is required to 

ee Fig. 5) and 

ius of the planet 

CHEOPS goes for small planets: transit of Earth‐size planet 

Figure 5: Simulation of a transiting Earth size-sized 

planet of 60 day period orbiting a G5 star of 8th Vmagnitude 

as observed by CHEOPS. Sampling time is 

1 minute and photon noise 100 ppm/minute. The red 

dots indicate 1h-averaged photometry. This light curve 

illustrates a transit detection with a S/Ntransit=10. 

80 ppm 

t G2V ≤ 0.5 days

surements of their mass and radius, but also a study of their atmospheric properties. 

ossible for planets orbiting bright enough stars to permit high signal-to-noise 

ric observations. This 

is drastically more 

-mass planets than for 

ng to the conclusion 

ew dozens of supertistically 

transit the 

within the solar 

will ever be suitable 

characterization with 

ts (e.g. Seager et al. 

has been nicely 

the case of the planet 

s eight Earth-masses 

y one transiting a star 

ed eye. First detected 

easurements, transits 

ed by the Spitzer and 

lescopes (Demory et 

t al. 2011), revealing 

size of ~2.1 Earththe 

brightness of its Figure 1: Mass-radius relationship for different bulk composition of 

, K=4), very high the planet (Adapted from Wagner et al. 2011) with superimposed 

ccultation photometry 

th Spitzer, leading to 

the thermal emission 

rth planet (Demory et 

known transiting planets where both the mass and the radius of the 

planet have been measured. The size of the boxes indicates the 1sigma 

error on these parameters. So far, in most cases the error bars 

are too large to obtain an unambiguous measurement of the bulk 

structure of the planets. 

Primary Objec-ve: measure mass‐radius relaRon for low‐mass planets…

le light sources in the universe. Time will be made available for this 

1'& 

d the large error 

tion for planets 

n to 1 MEarth is 

PS will provide a 

by significantly 

ize as well as the 

ts. We anticipate 

gnificant intrinsic 

relationship. This 

ich diversity of 

formation and 

ms, and thus can 

odels of these 

io, the core of a 

mass before it is 

ay fashion. This 

many physical 

portant of which 

cretion. 

mean planetary 

… to determine the bulk structure of planets 

0% (10 -4 %) 

Figure 2: Radius of a hot rocky planet surrounded by a 

water atmosphere. The composition of the planetary core 

is similar to the one of the Earth, and the mass of the 

water envelope is indicated on the figure (in percentage 

of the total planetary mass). Adapted from Valencia et 

al. (2010).

Figure 12: Initial mechanical concept for the telescope and the lightweighted primary mirror. 

elevate and stabilize the temperature. A further key iss 

to be the shrinkage by CFRP due to moisture release 

Table 7: Current payload mass breakdown 

The mechanical concept is shown in Fig. 12. The preliminary mass breakdown is shown in Table 7. 

The structure is to be manufactured out of 33.5 a carbon-fibre cm (F/8) reinforced CFRP polymer (≥50%) structure (CFRP; heritage 5*9#0!%,-/01!EK8! 

from RUAG Space Switzerland) with Zerodur reflective Zerodur mirrors + with Ag protected silver coatings /*G7*-6-9$.! ! 

K#L,#9*+! ;13! ;12! 

@:96+!A#QQ06!F$$6GH0I! ;;13! ;C12! 

5*9#0!

platforms would be capable of delivering the necessary performance. 

!"2 3456/*4+40'1, 

!"2"7 89:,*456/*4+40'1,16++&*;, 

The key requirements for the spacecraft can be traced 

to the photometric performance required by the 

CHEOPS mission: 

AOCS / Pointing stability: AOCS shall provide 8arcsec 

stability rms (or better) over 10 hour 

observations. The S/C shall be 3-axis stabilized but 

nadir locked. 

expertise for addressing the AOCS design during the Phase A and identifying the modifications to the 

Thermal stability: Thermal SSTL-150 standard interface equipment between necessary to meet the pointing requirements is present in Italy. For 

spacecraft bus and detector instance, assembly Thales Alenia shall Space be Italy stable recently performed as Prime Contractor the Definition Phase of 

Figure 12: Initial mechanical concept for the telescope and the lightweighted PLATO, a mission primary with mirror. similar scientific objectives, having in particular the responsibility of the 

(!T=1K, TBC) and provide whole a AOCS location architecture for the (including payload the interface with the payload telescopes), operational modes 

The mechanical concept is shown in Fig. radiator 12. The so preliminary that the radiator mass design, breakdown always sensors/actuators faces is identification, cold shown space in Table performance 7. analysis, simulation and budgets. This capability 

(no flux from Earth or Sun). also exists in Sweden. 

The structure is to be manufactured out of 33.5 a carbon-fibre cm (F/8) reinforced CFRP polymer (≥50%) structure (CFRP; heritage 

The orbit control system consists of a xenon-based resistojet propulsion system with a total delta-v 

from RUAG Space Switzerland) with Power: Zerodur The reflective spacecraft Zerodur mirrors shall capability provide + with Ag of 36 protected 54W m/s. The continuous gaseous silver nature coatings of the xenon propellant avoids issues associated with 

(heritage e.g. SESO, Selex Galileo). The power primary for will instrument be lightweighted operations propellant to slosh, at least and is thus 50% appropriate. to reduce Although total a low level of orbit maintenance propellant may be 

required to maintain altitude during the operational phase of the mission, the majority of this 

mass. The telescope must be baffled to Data: reduce The stray spacecraft light (primarily shall provide from the at least Earth). 1GBit/day Concerns over 

propulsion capability is likely to be used to lower the orbit at the end of life, hence ensuring 

cleanliness and contamination lead to introduction downlink of a door cover compliance (which with is light debris and mitigation dust standards. tight). It An is estimated delta-v of

Fourtney et al. 

2008 

onto the primary mirror is the largest source of 

Figure 10: PSF of the preliminary optical design. 

stray light in the current baffle design. By 

increasing the length of the baffle, both scattering from the spider and scattering from the baffle to the 

secondary mirror are minimised. Combined with an inner and outer baffling system (cf. CoRoT) the 

major stray light requirement (reaching < 1 ph/px/s) can be met. A comparison of the point source 

transmission functions of CoRoT, the Cassini orbiter narrow angle camera, and our preliminary design 

is made in Fig. 11. At this stage, black coatings with 2% hemispherical (isotropic) reflectivity may be 

straylight main noise culprit 

single frame-transfer !T !10 mK 

back-side illuminated @ 

CCD 0.4-1.1 µm 

T < 233 K 

The 13 μm pixel 1k x 1k CCD 

(baseline = e2v CCD47‐20 AIMO) 

is used with a mid‐band coaRng to enhance the 

quantum efficiency. 

Replace the CCD detector w. 

Hawaii-2RG 

Beam splitter will provide two 

images on the same detector 

0.4–1.05 µm and 1.05–1.7 µm 

required together with knife-edge radii of the baffle vanes of 100 µm. The stray light distribution and 

its variability on the focal plane have been simulated to evaluate whether the correction requirement 

can be met. Preliminary results 

Table 4: Working error budget for the CHEOPS Instrument 

System. 

Quantity Bright Intermed. 

Faint Very 

faint 

Magnitude (G type star) 8 10 12 12.5 

Texp per image [s] 10 10 10 10 

%age FW 26% 4.1% 0.65% 0.41% 

Shot-noise [ppm] 224.7 563.3 1418.1 1785.6 

Read noise [ppm] 14.6 92.4 582.9 924.0 

Quantize noise [ppm] 3.6 22.7 144.0 228.3 

Flat-field (FF) 4 [ppm] 14.8 14.8 14.8 14.8 

Zodiacal light, dark noise 

post-subtraction 1 [ppm] 

17.7 112.45 709.3 1124.5 

Gain stability [ppm] 5.0 5.0 5.0 5.0 

QE stability [ppm] 5.0 5.0 5.0 5.0 

Dark current var. [ppm] 0 0 0 0 

Resid. elec. noise [ppm] 0 1.6 10.1 15.9 

Timing error [ppm] 2 2 2 2 

Stray light 2 [ppm] 1.8 11.3 71.5 114.0 

Cosmic ray 3 [ppm] 1.3 1.3 1.3 1.3 

Total S/N single image 

[ppm] 

225.4 573.1 1542.0 2027.0 

Total S/N 1 min [ppm] 101.0 256.6 692.7 912.4 

Total S/N 1 h on target 

[ppm] 

Total S/N 3 h on target 

[ppm] 

14.3 33.7 110.4 158.6 

10.4 22.5 87.3 131.3 

1 We assume zodiacal light at the level determined by WFC3, which 

can be subtracted perfectly. 2 Assuming 99.6% correction of a level 

set 1.1 e/s/px (comparable to COROT) 3 Cosmic ray flux taken from 

WFC3 and modified for this detector. 4 The flat-field error relates to 

the 8 arcsec jitter requirement combined with an assumed 

knowledge accuracy on the FF. White coloured boxes = input stellar 

fluxes; Green = Gaussian noises; Yellow = design and calibrated; 

Red = post-factum calibration; White (below) = total accuracy 

indicate that stray the light correction 

will be sufficient for the targeted 

photometric accuracy. 

The S/N budget (see Table 4) also 

reveals the importance of thermal 

stability of the CCD and proximity 

electronics (including the gain). 

Based upon similar devices (e.g. the 

e2v detector currently flying on 

Rosetta/OSIRIS), the CCD needs to 

be held at constant temperature to an 

accuracy of ~10 mK for the duration 

of one observation, to limit its noise 

contribution to ~5 ppm. The detector 

is connected to an external radiator, 

which will give an operating 

temperature of

We anticipate 6 planets of that kind will be detected by NGTS on stars brighter than V < 12 

magnitude. Note that the NGTS targeting scenario is flexible enough to be optimized to CHEOPS 

Target Selection 

pointing capabilities. 

Table 2: Expected number of transiting planets to be detected by NGTS after 5 years of observation in 

different stellar magnitude and planet radius bins. This corresponds to a survey of 10% of the southern 

sky. The color of the box indicates the estimated CHEOPS capabilities to successfully observe these 

objects (Green box: Light curve measured by CHEOPS with S/Ntransit achievable with CHEOPS and methods 

required: Green – S/Ntransit > 30; Light Green: S/Ntransit > 30 achievable but requires 4 to 10 transits to be co-added; 

Yellow - detectable but S/Ntransit only > 10. 

Radius: R

Figure 4: Transiting planets from different surveys: Planet radius vs. V-magnitude of the host star. 

Pink diamond: ground based transiting planet (mostly WASP and HAT), Green: radial velocity survey 

planets that have been found transiting their star; Blue triangles: CoRoT transiting planets, Violet 

square: Kepler transiting planet candidates (only a handful have been confirmed). The orange area 

indicates the search domain of NGTS, the next generation ground transit search. The green area 

indicates the search area of the precise Doppler search programs like HARPS. This instrument will 

provide measurements of planet masses to 20% accuracy for objects lying to the right of the black 

solid line (assuming the period and ephemerids are known and 20 measurements are available) 

provided they have an Earth-like mean density. The dotted black line gives the limit for a mean density 

corresponding to water-ice planets. The solid red curve indicates the CHEOPS limits for S/Ntransit=10 

and the dotted red indicates the CHEOPS limit for S/Ntransit=30.

Figure 7: Mollweide projection of the accessible celestial sphere for CHEOPS observations in the 

ICRF. It shows the total length of time (in hours) a given area of the celestial sphere can be observed 

over a one year period from the SSO 6am/6pm at 800km orbit. Observation time-spans of shorter than 

60 mins have not been taken into account. Constraints taken into account are obscuration of the target 

by Earth, relative sun angle and restrictions on reflected sun light from Earth. 

15 

800 km Solar Synchronous Orbit 6:00/18:00 

near day-night terminator

While this orbit satisfies the main requirements, other orbits would provide even better solutions. For 

example, the option called “GTO extended” would allow a larger fraction of the sky to be seen albeit 

at the cost of increased technical effort and budget, see Table 3. 

In either case, the launch will be a shared launch: CHEOPS will not utilize the full capacity of a 

Figure VEGA 7: class Mollweide launch vehicle. projection The of baseline the accessible mission duration celestial is sphere 3.5 years for nominal CHEOPS mission. observations in the 


!"# $%&'() 


60 We mins performed have not a trade been taken off study into for account. different Constraints orbit types taken (SSO, into GTO, account Molniya are obscuration and L2). We of the compared target 

by the Earth, following relative parameters: sun angle and Observable restrictions sky, on radiation, reflected sun eclipses, light from telecommunication, Earth. cost, thermal 

environment and needed propulsion. The main driver, which determines the orbits available, is to meet 15 

the minimum required fraction of observable sky within the budgetary envelope available. 

Table 3: Orbit characteristics for the baseline and two options. *For the GTO extended, all targets can be 

observed at least 6 hours uninterrupted during the 3.5 year mission. 

Orbit characteristics SSO 800 

(baseline) 

SSO 

1200 

GTO 

extended 

Perigee altitude [km] 800 1200 10000 

Apogee altitude [km] 800 1200 35943 

Orbital period [min] 101 109 834 

Mean local time of ascending node [h] 6 a.m. 6 a.m. - 

Percentage of the sky available for a minimum total duration of 15 days 

27% 47% * 

per year and target. Maximum interruption time is 20 minutes per orbit. 


per year and target. Maximum interruption time is 50 minutes per orbit 

(for SSO). 

58% 69% 100% 

baseline

α Cen 

While this orbit satisfies the main requirements, other orbits would provide even better solutions. For 

example, the option called “GTO extended” would allow a larger fraction of the sky to be seen albeit 

at the cost of increased technical effort and budget, see Table 3. 

In either case, the launch will be a shared launch: CHEOPS will not utilize the full capacity of a 

Figure VEGA 7: class Mollweide launch vehicle. projection The of baseline the accessible mission duration celestial is sphere 3.5 years for nominal CHEOPS mission. observations in the 


!"# $%&'() 


60 We mins performed have not a trade been taken off study into for account. different Constraints orbit types taken (SSO, into GTO, account Molniya are obscuration and L2). We of the compared target 

by the Earth, following relative parameters: sun angle and Observable restrictions sky, on radiation, reflected sun eclipses, light from telecommunication, Earth. cost, thermal 

environment and needed propulsion. The main driver, which determines the orbits available, is to meet 15 

the minimum required fraction of observable sky within the budgetary envelope available. 

Table 3: Orbit characteristics for the baseline and two options. *For the GTO extended, all targets can be 

observed at least 6 hours uninterrupted during the 3.5 year mission. 

Orbit characteristics SSO 800 

(baseline) 

SSO 

1200 

GTO 

extended 

Perigee altitude [km] 800 1200 10000 

Apogee altitude [km] 800 1200 35943 

Orbital period [min] 101 109 834 

Mean local time of ascending node [h] 6 a.m. 6 a.m. - 


27% 47% * 

per year and target. Maximum interruption time is 20 minutes per orbit. 


per year and target. Maximum interruption time is 50 minutes per orbit 

(for SSO). 

58% 69% 100% 

baseline

Launch Vehicles & Service 

(passenger flights) 

Ariane 5/Soyuz Dnepr ‐ ROCKOT Vega 

GTO‐extended & L2 LEO 4500 kg LEO 1950 kg LEO 1500 kg 

ISS 3200 kg SSO 1200 kg 

TLI 550 kg

Baseline Mission duration 3.5 years 

2 days observaRon of 200 targets with 50% orbit interrupRon 800 days 

NGTS targets need 12 hours 50 targets 1 transit (25 days + 20%) 30 days 

50 targets 4 transits (100 days + 20%) 120 days 

5 targets 10 transits (25 days + 20%) 30 days 

5 hot Jups reflected light 5 Rmes 15 days 75 days 

Observatory program (open access) 150 days 

SummaRon: 1205 days

EEPROM available 

boot loader 

4M x 8, used for storage of 

downlink 

App-S/W 

DPM clock rate 25 MHz 

Table 5: Downlink rates required. 1 Assuming 4 x 15 min 

downlink at 720 kbit/s. 

Image size 200 px x 200 px 

ADC resolution 16 bit 

Frame frequency 5 images/min 

Downlink frequency 1 image/min 

HK rate 100 bit/s 

Data rate to ground required 0.9 Gb/day 

Maximum s/c to ground 1 2.6 Gb/day 

i 

d 

T 

T 

c 

G 

e 

w 

p 

D 

( 

t 

f 

a

s/c requirements 

AOCS / PoinFng Stability 3‐axis stabilized, nadir locked; ≤ 8 arcsec over 10 hours 

Thermal Stability bus ‐ detector assembly δT = 1 K; radiator toward cold space 

Power 54 W conRnuously 

Data downlink ≥ 1 Bbit/day

• Sun shield: CGS and SSTL offer to design sun shield. Flight heritage from Odin mission. 

On the payload side, critical components are the FPA, the readout electronics, the thermal control, and 

the baffle in order to reach the required example 10 ppm platform 

photometric precision. The proposing team has 

heritage from the CoRoT mission in building the readout electronics, the FPA, and the baffle. RUAG 

has heritage from the TROPOMI mission for the thermal control. 

The qualification status of all payload and s/c components is demonstrated in Table 9 and Table 10. 

Table 9: Qualification Status List for Platform using the SSTL-150 platform as an example. The required 

changes for a GTO orbit are also indicated (A: heritage item, B: heritage item used with modifications, C: 

development required) 

Item LE GTO Remarks 

TTC Comms O A B Baseline system well established – GTO would require different antennas and 

X-Band Tx A B more power 

Structure C C Dedicated structure in both cases 

ADCS B C Baseline system may require additional gyro – GTO would require 

hardened components 

OBDH A B Baseline system well established – GTO would require hardened components 

Power B C Baseline system would require more solar array area & sun shield 

configuration – GTO requires radiation hardening 

Propulsion A C Baseline system well established – GTO requires dedicated development 

Harness B B Some elements required in both cases to accommodate CHEOPS payload 

Thermal Control C C Sunshield solution required in both cases 

Table 10: Qualification Status List for Payload: (A: heritage item, B: heritage item used with 

modifications, C: development required) 

Item QS Remarks 

DPU B Graz builds similar DPU for solar orbiter. TRL 6 

Telescope C Afocal on-axis design. Preliminary design done. Stray light (PST) and jitter 

sensitivity (PSF shape) requirements are met.

ADCS B C Baseline system may require additional gyro – GTO would require 

hardened components 

OBDH 

Power 

A 

B 

B 

C 

Baseline system well established – GTO would require hardened components 

payload Baseline system - would baseline 

require more solar array area & sun shield 

configuration – GTO requires radiation hardening 

Propulsion A C Baseline system well established – GTO requires dedicated development 

Harness B B Some elements required in both cases to accommodate CHEOPS payload 

Thermal Control C C Sunshield solution required in both cases 

Table 10: Qualification Status List for Payload: (A: heritage item, B: heritage item used with 

modifications, C: development required) 

Item QS Remarks 

DPU B Graz builds similar DPU for solar orbiter. TRL 6 


sensitivity (PSF shape) requirements are met. 

Readout electronics B Heritage from CoRoT, Kepler, TRL 7 

Thermal control FPA B Heritage from CoRoT, Kepler, TRL 7 

FPA B Heritage from CoRoT, Kepler, TRL 7 

CCD B Heritage from CoRoT, Kepler, different model, TRL 7 

Baffle B Heritage from CoRoT, Kepler; TRL 8 

A note relating to the NIR option: Efforts continue to investigate the suitability of extant short-wave 

cut-off near-IR arrays for an extension of the baseline CHEOPS mission. Detectors currently under 

consideration include the new generation of Hawaii-2RG devices with the SIDECAR ASIC electronic 

controllers. These devices have achieved TRL-6 as defined by NASA (Beletic et al. 2008) and are key 

components of the NIRCam (Green et al. 2010) and NIRISS (Doyon et al. 2010) instruments (with 2.5 

micron cut-off devices in the short-wave channels) for the NASA/ESA James Webb Space Telescope 

planned for launch in 2018. Recent laboratory work involving 1.7 micron cut-off devices suggests


sensitivity (PSF shape) requirements are met. 

payload – extended (IR) 

Readout electronics B Heritage from CoRoT, Kepler, TRL 7 

Thermal control FPA B Heritage from CoRoT, Kepler, TRL 7 

FPA B Heritage from CoRoT, Kepler, TRL 7 

CCD B Heritage from CoRoT, Kepler, different model, TRL 7 

Baffle B Heritage from CoRoT, Kepler; TRL 8 

A note relating to the NIR option: Efforts continue to investigate the suitability of extant short-wave 

cut-off near-IR arrays for an extension of the baseline CHEOPS mission. Detectors currently under 

consideration include the new generation of Hawaii-2RG devices with the SIDECAR ASIC electronic 

controllers. These devices have achieved TRL-6 as defined by NASA (Beletic et al. 2008) and are key 

components of the NIRCam (Green et al. 2010) and NIRISS (Doyon et al. 2010) instruments (with 2.5 

micron cut-off devices in the short-wave channels) for the NASA/ESA James Webb Space Telescope 

planned for launch in 2018. Recent laboratory work involving 1.7 micron cut-off devices suggests 

they may possess the performance characteristics required to satisfy the needs of the CHEOPS mission 

(Clanton et al. 2012 in press). We continue to explore this option and further laboratory investigations 

are underway in our consortium. 

! ! 

24

CHaracterizingExOPlanet Satellit 

Interested Parties - contact 

!"#$%&$'()$%*+,' 

Mission Coordinator: 

Prof. Willy Benz 



Sidlertrasse 5 

3012 Bern 

Switzerland 

e-mail: willy.benz@space.unibe.ch 

Proposing Team Members: 

Country Institute 

A Institut für Weltraumforschung, Graz,

end

cheops - Leiden Observatory

Create successful ePaper yourself

Delete template?

Save as template?