As the performance of space based astrophysics observatories is directly limited by the size of the spacecraft and the telescope it carries, current missions are reaching the limit of the launchers’ ...capabilities. Before considering to develop larger launchers or to implement formation flying missions or in orbit assembly, the possibility of deploying structures once in orbit is an appealing solution. This paper describes the different technologies currently available to develop deployable structures, with an emphasis on those that can allow achieving long focal lengths. The review of these technologies is followed by a comparison of their performance and a list of trade-off parameters to be considered before selecting the most appropriate solution for a given application. Additionally, a preliminary structural analysis was performed on a typical deployable structure, applied to the case of a mission requiring a 20
m focal length extension. The results show that by using several deployable masts, it is possible to build stiff deployed structures with eigen frequencies over 1
Hz. Finally, a discussion on metrology concepts is provided, as knowledge of the relative position between the telescope and the deployed focal plane instruments is critical.
ESA technology reference studies are used as a process to identify key technologies and technical challenges of potential future missions not yet in the science programme. This paper reports on the ...study of the Fundamental Physics Explorer (FPE), a re-usable platform targeted to small missions testing fundamental laws of physics in space. The study addresses three specific areas of interest: special and general relativity tests based on atomic clocks, experiments on the Weak Equivalence Principle (WEP), and studies of Bose–Einstein condensates under microgravity conditions. Starting from preliminary science objectives and payload requirements, three reference missions in the small/medium class range are discussed, based on a re-adaptation of the LISA Pathfinder spacecraft. A 700/3600km elliptic orbit has been selected to conduct clock tests of special and general relativity, a 700km circular orbit to perform experiments on the Weak Equivalence Principle and to study Bose–Einstein condensates, each mission being based on a three-axis stabilised spacecraft. It was determined that adaptation of LISA Pathfinder would be required in order to meet the demands of the FPE missions. Moreover it was established that specific payload and spacecraft technology development would be required to realise such a programme.
This paper describes the design, development and performance of the engineering model double adiabatic demagnetization refrigerator (dADR) built and tested under contract to the European Space Agency ...for its former mission XEUS (now IXO). The dADR operates from a 4
K bath and has a measured recycle and hold time (with a parasitic load of 2.34
μW) at 50
mK of 15
h and 10
h, respectively. It is shown that the performance can be significantly improved by operating from a lower bath temperature and replacing the current heat switches with tungsten magnetoresistive (MR) heat switches, which significantly reduce the parasitic heat load. Performing the latter gives an anticipated recycle and hold time of 2 and 29
h (with a 1
μW applied heat load in addition to the parasitic load), respectively. Such improved performance allows for a reduction in mass of the dADR from 32
kg to 10
kg by operating from a 2.5
K bath (which could be reduced further by optimising the magnet design). Ultimately, continuous operation could be achieved by linking two dADRs to a common detector stage and operating them alternately. Based on this design the mass of the continuous ADR is estimated to be about 4.5
kg.
ABSTRACT
CHEOPS (CHaracterising ExOPlanet Satellite) is an ESA S-class mission that observes bright stars at high cadence from low-Earth orbit. The main aim of the mission is to characterize ...exoplanets that transit nearby stars using ultrahigh precision photometry. Here, we report the analysis of transits observed by CHEOPS during its Early Science observing programme for four well-known exoplanets: GJ 436 b, HD 106315 b, HD 97658 b, and GJ 1132 b. The analysis is done using pycheops, an open-source software package we have developed to easily and efficiently analyse CHEOPS light-curve data using state-of-the-art techniques that are fully described herein. We show that the precision of the transit parameters measured using CHEOPS is comparable to that from larger space telescopes such as Spitzer Space Telescope and Kepler. We use the updated planet parameters from our analysis to derive new constraints on the internal structure of these four exoplanets.
Context.
55 Cnc e is a transiting super-Earth (radius 1.88
R
⊕
and mass 8
M
⊕
) orbiting a G8V host star on a 17-h orbit.
Spitzer
observations of the planet’s phase curve at 4.5 μm revealed a ...time-varying occultation depth, and MOST optical observations are consistent with a time-varying phase curve amplitude and phase offset of maximum light. Both broadband and high-resolution spectroscopic analyses are consistent with either a high mean molecular weight atmosphere or no atmosphere for planet e. A long-term photometric monitoring campaign on an independent optical telescope is needed to probe the variability in this system.
Aims.
We seek to measure the phase variations of 55 Cnc e with a broadband optical filter with the 30 cm effective aperture space telescope CHEOPS and explore how the precision photometry narrows down the range of possible scenarios.
Methods.
We observed 55 Cnc for 1.6 orbital phases in March of 2020. We designed a phase curve detrending toolkit for CHEOPS photometry which allowed us to study the underlying flux variations in the 55 Cnc system.
Results.
We detected a phase variation with a full-amplitude of 72 ± 7 ppm, but did not detect a significant secondary eclipse of the planet. The shape of the phase variation resembles that of a piecewise-Lambertian; however, the non-detection of the planetary secondary eclipse, and the large amplitude of the variations exclude reflection from the planetary surface as a possible origin of the observed phase variations. They are also likely incompatible with magnetospheric interactions between the star and planet, but may imply that circumplanetary or circumstellar material modulate the flux of the system.
Conclusions.
This year, further precision photometry of 55 Cnc from CHEOPS will measure variations in the phase curve amplitude and shape over time.
Context.
Gas giants orbiting close to hot and massive early-type stars can reach dayside temperatures that are comparable to those of the coldest stars. These ‘ultra-hot Jupiters’ have atmospheres ...made of ions and atomic species from molecular dissociation and feature strong day-to-night temperature gradients. Photometric observations at different orbital phases provide insights on the planet’s atmospheric properties.
Aims.
We aim to analyse the photometric observations of WASP-189 acquired with the Characterising Exoplanet Satellite (CHEOPS) to derive constraints on the system architecture and the planetary atmosphere.
Methods.
We implemented a light-curve model suited for an asymmetric transit shape caused by the gravity-darkened photosphere of the fast-rotating host star. We also modelled the reflective and thermal components of the planetary flux, the effect of stellar oblateness and light-travel time on transit-eclipse timings, the stellar activity, and CHEOPS systematics.
Results.
From the asymmetric transit, we measure the size of the ultra-hot Jupiter WASP-189 b, R
p
= 1.600
−0.016
+0.017
R
J
, with a precision of 1%, and the true orbital obliquity of the planetary system, Ψ
p
= 89.6 ± 1.2deg (polar orbit). We detect no significant hotspot offset from the phase curve and obtain an eclipse depth of δ
ecl
= 96.5
−5.0
+4.5
ppm, from which we derive an upper limit on the geometric albedo:
A
g
< 0.48. We also find that the eclipse depth can only be explained by thermal emission alone in the case of extremely inefficient energy redistribution. Finally, we attribute the photometric variability to the stellar rotation, either through superficial inhomogeneities or resonance couplings between the convective core and the radiative envelope.
Conclusions.
Based on the derived system architecture, we predict the eclipse depth in the upcoming Transiting Exoplanet Survey Satellite (TESS) observations to be up to ~165 ppm. High-precision detection of the eclipse in both CHEOPS and TESS passbands might help disentangle reflective and thermal contributions. We also expect the right ascension of the ascending node of the orbit to precess due to the perturbations induced by the stellar quadrupole moment
J
2
(oblateness).
Context.
Ultra-short period planets undergo strong tidal interactions with their host star which lead to planet deformation and orbital tidal decay.
Aims.
WASP-103b is the exoplanet with the highest ...expected deformation signature in its transit light curve and one of the shortest expected spiral-in times. Measuring the tidal deformation of the planet would allow us to estimate the second degree fluid Love number and gain insight into the planet’s internal structure. Moreover, measuring the tidal decay timescale would allow us to estimate the stellar tidal quality factor, which is key to constraining stellar physics.
Methods.
We obtained 12 transit light curves of WASP-103b with the CHaracterising ExOplanet Satellite (CHEOPS) to estimate the tidal deformation and tidal decay of this extreme system. We modelled the high-precision CHEOPS transit light curves together with systematic instrumental noise using multi-dimensional Gaussian process regression informed by a set of instrumental parameters. To model the tidal deformation, we used a parametrisation model which allowed us to determine the second degree fluid Love number of the planet. We combined our light curves with previously observed transits of WASP-103b with the
Hubble
Space Telescope (HST) and
Spitzer
to increase the signal-to-noise of the light curve and better distinguish the minute signal expected from the planetary deformation.
Results.
We estimate the radial Love number of WASP-103b to be h
f
= 1.59
−0.53
+0.45
. This is the first time that the tidal deformation is directly detected (at 3
σ
) from the transit light curve of an exoplanet. Combining the transit times derived from CHEOPS, HST, and
Spitzer
light curves with the other transit times available in the literature, we find no significant orbital period variation for WASP-103b. However, the data show a hint of an orbital period increase instead of a decrease, as is expected for tidal decay. This could be either due to a visual companion star if this star is bound, the Applegate effect, or a statistical artefact.
Conclusions.
The estimated Love number of WASP-103b is similar to Jupiter’s. This will allow us to constrain the internal structure and composition of WASP-103b, which could provide clues on the inflation of hot Jupiters. Future observations with
James Webb
Space Telescope can better constrain the radial Love number of WASP-103b due to their high signal-to-noise and the smaller signature of limb darkening in the infrared. A longer time baseline is needed to constrain the tidal decay in this system.
Cryogenics has made a remarkable amount of progress over the last 15 years. The increased reliability and simplicity of operations of cryogenic equipment have allowed to install and to successfully ...operate them onboard spacecrafts. At the same time, the improved performance of cryogenic devices, such as sensors and cold electronics, has drastically enlarged their utilisation, creating new perspectives for space-based applications. In this paper we provide an up-to-date review of the non-military space missions making use of cryogenic instrumentation and a summary of the present and envisaged applications of cryogenic equipment in space. The impact of cryogenics on the spacecraft system design and the main technical solutions presently adopted are also discussed. Finally, this paper provides an outlook on near- and mid-term future activities involving cryogenics in space and on the related technology development, with particular emphasis on the work carried out by the European Space Agency.
Peacock et al report a super-conducting device that can overcome limitations associated with decreasing wavelengths, and which has performance characteristics far superior to existing photon counting ...systems.
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