The Herschel Space Observatory was the fourth Cornerstone mission of ESA’s Horizon 2000 programme, and a €1Bclass far infrared space observatory. The satellite and mission were developed over an approximately 10-year period before launch in 2009 and highly successful operation for approximately four years. A Post-Operations programme continued until 2017 (and with little resources even until 2019) in order to complete the data processing, calibration and documentation activities and to populate the Herschel Science Archive with the final data products and documentation. The Herschel Science Team, which oversaw the mission over a nearly 20-year period from late 1998 until its 61st and final meeting in late 2017, has conducted a comprehensive lessons learned review of the project from start to finish, encompassing all aspects of the endeavour – programmatics and management of the spacecraft, instrument consortia and ground segment; instrument development and testing; spacecraft implementation; ground segment and operations preparation pre-launch, in-flight operation and post-operations; science management and user support; and communications. Science is not addressed here except in general terms – this is not a scientific assessment. Focusing on generic features of the mission and its management, organisation, and technical design that have potential applications and relevance to future space projects, we have identified and assessed a number of aspects in which the Herschel experience can provide valuable lessons, both positive and negative, to aid the effective development and success of future missions, especially ones that are comparable in magnitude and complexity. We outline the main findings and conclusions of this Lessons Learned exercise.
The Atmospheric Remote-Sensing Infrared Exoplanet Large-survey, ARIEL, has been selected to be the next (M4) medium class space mission in the ESA Cosmic Vision programme. From launch in 2028, and during the following 4 years of operation, ARIEL will perform precise spectroscopy of the atmospheres of ~1000 known transiting exoplanets using its metre-class telescope. A three-band photometer and three spectrometers cover the 0.5 µm to 7.8 µm region of the electromagnetic spectrum.
This paper gives an overview of the mission payload, including the telescope assembly, the FGS (Fine Guidance System) - which provides both pointing information to the spacecraft and scientific photometry and low-resolution spectrometer data, the ARIEL InfraRed Spectrometer (AIRS), and other payload infrastructure such as the warm electronics, structures and cryogenic cooling systems.
Ariel, the “atmospheric remote sensing infrared exoplanet large survey” mission, is the European Space Agency’s Cosmic Vision M4 (medium-class number 4) science mission. It has recently gone through an implementation approval (“adoption”), with a planned launch in 2029. Ariel, together with two other M4 candidate missions (THOR and XIPE), was recommended in June 2015 to enter an assessment study, consisting of a Phase 0 at the ESA internal Concurrent Design Facility study followed by a Phase A with parallel industrial studies. The Phase A was concluded in March 2018 with the selection of Ariel as the M4 mission endorsed by the ESA Science Programme Committee (SPC). Phase B1 was subsequently initiated, and was concluded by the Mission Adoption Review in mid-2020, followed by the formal adoption of Ariel in November 2020 by the SPC. Ariel is a survey-type mission dedicated to the characterisation of exoplanets by performing a chemical census. Using the differential technique of transit/eclipse spectroscopic observations, Ariel will obtain transmission and/or emission spectra of the atmospheres of a large (~1000) and diverse sample of known exoplanets covering a wide range of masses, densities, equilibrium temperatures, orbital properties and host-star characteristics. This will include hot Jupiters to warm Super-Earths, orbiting A to M spectral class host stars. This paper reports on the Ariel Phase 0/A/B1 study, including the conclusions of the reviews that were conducted in 2020 to close the study and support the adoption process.
Placed on the L2 Lagrangian point, Herschel operates in the spectral range between 80 and 670 μm wavelength and is devoted to astronomical investigations in the far-infrared, sub-millimetre and millimetre wavelengths. The Herschel Telescope is an “all Silicon Carbide” Telescope, based on a 3.5-m-diameter Cassegrain design. The driving requirements are the large diameter (3,5m), the WFE to be kept below 6μrms despite the operational temperature (70K), and finally the mass to be kept below 300kg. The size of the Telescope has put some challenges in the manufacturing and the tests facilities installations. At this stage, the major critical phase which is the brazing of the primary mirror has successfully been passed. The development and manufacturing of the Herschel Telescope is part of the Herschel Planck program funded by the European Space Agency (ESA).
The Atmospheric Remote-Sensing Infrared Exoplanet Large-survey, ARIEL, has been selected to be the next M4 space mission in the ESA Cosmic Vision programme. From launch in 2028, and during the following 4 years of operation, ARIEL will perform precise spectroscopy of the atmospheres of about 1000 known transiting exoplanets using its metre-class telescope, a three-band photometer and three spectrometers that will cover the 0.5 µm to 7.8 µm region of the electromagnetic spectrum. The payload is designed to perform primary and secondary transit spectroscopy, and to measure spectrally resolved phase curves with a stability of < 100 ppm (goal 10 ppm). Observing from an L2 orbit, ARIEL will provide the first statistically significant spectroscopic survey of hot and warm planets. These are an ideal laboratory in which to study the chemistry, the formation and the evolution processes of exoplanets, to constrain the thermodynamics, composition and structure of their atmospheres, and to investigate the properties of the clouds.
The Atmospheric Remote sensing Infrared Exoplanet Large survey (ARIEL) mission is an M-class mission candidate
within the science program Cosmic Vision of the European Space Agency (ESA). It was selected in June 2015 as one of
three candidates to enter an assessment phase (phase 0/A). This process involves the definition of science and mission
requirements as well as a preliminary model payload, and an internal Concurrent Design Facility (CDF) study providing
the input to parallel industrial studies (in progress since 2016). After this process, the three candidates will be reviewed
and in mid-2017 one of them will be selected as the M4 mission for launch in 2026.
ARIEL is a survey-type mission dedicated to the characterisation of exoplanetary atmospheres. Using the differential
technique of transit spectroscopy, ARIEL will obtain transmission and/or emission spectra of the atmospheres of a large
and diverse sample of known exoplanets (~500) covering a wide range of masses, densities, equilibrium temperatures,
orbital properties and host-star characteristics. This will include hot Jupiters to warm Super-Earths, orbiting M5 to F0
This paper describes critical requirements, and reports on the results of the Concurrent Design Facility (CDF) study that
was conducted in June / July 2015, providing a description of the resulting spacecraft design. It will employ a 0.7 m x 1.1
m off-axis three mirror telescope, feeding four photometric channels in the VNIR range (0.5-1.95 μm) and an IR
spectrometer covering 1.95-7.8 μm.
The Atmospheric Remote-Sensing Infrared Exoplanet Large-survey (ARIEL) is one of the three candidate missions selected by the European Space Agency (ESA) for its next medium-class science mission due for launch in 2026. The goal of the ARIEL mission is to investigate the atmospheres of several hundred planets orbiting distant stars in order to address the fundamental questions on how planetary systems form and evolve.
During its four (with a potential extension to six) years mission ARIEL will observe 500+ exoplanets in the visible and the infrared with its meter-class telescope in L2. ARIEL targets will include gaseous and rocky planets down to the Earth-size around different types of stars. The main focus of the mission will be on hot and warm planets orbiting close to their star, as they represent a natural laboratory in which to study the chemistry and formation of exoplanets.
The ARIEL mission concept has been developed by a consortium of more than 50 institutes from 12 countries, which include UK, France, Italy, Germany, the Netherlands, Poland, Spain, Belgium, Austria, Denmark, Ireland and Portugal. The analysis of the ARIEL spectra and photometric data in the 0.5-7.8 micron range will allow to extract the chemical fingerprints of gases and condensates in the planets’ atmospheres, including the elemental composition for the most favorable targets. It will also enable the study of thermal and scattering properties of the atmosphere as the planet orbit around the star.
ARIEL will have an open data policy, enabling rapid access by the general community to the high-quality exoplanet spectra that the core survey will deliver.
Herschel is the next astronomy mission in the European Space Agency (ESA) science programme. It is currently in
the final stages of assembly and verification in ESA's ESTEC facility in Noordwijk, and is scheduled to be flown to
the launch site at Europe's Spaceport in Kourou later this year. Herschel will carry a 3.5 metre diameter passively
cooled Cassegrain telescope which is the largest of its kind and utilises novel silicon carbide technology. The
science payload comprises three instruments: two direct detection cameras/medium resolution spectrometers,
PACS and SPIRE, and a very high resolution heterodyne spectrometer, HIFI. The focal plane units are housed
inside a superfluid helium cryostat based on ISO legacy. Herschel will be launched by an Ariane 5 ECA together
with the Planck satellite into a transfer trajectory towards the operational orbit around L2. When operational
Herschel will provide unprecedented observational opportunities in the 55-672 μm spectral range, much of which
has never before been accessible from a space observatory. It is an observatory facility available to the worldwide
astronomical community, nominally almost 20,000 hours will be available for astronomy, 32% is guaranteed time
and the remainder is open to the general astronomical community through a standard competitive proposal
procedure. The initial Key Programme Announcement of Opportunity (AO) was issued in Feb 2007. Both
the guaranteed and open time Key Programmes have been selected and are introduced, and future observing
opportunities are outlined.
Placed on the L2 Lagrangian point, Herschel operates in the spectral range between 80 and 670 μm wavelength and is devoted to astronomical investigations in the far-infrared, sub-millimetre and millimetre wavelengths. The Herschel Telescope is an "allSilicon Carbide" Telescope, based on a 3.5-m-diameter Cassegrain design. The driving requirements are the large diameter (3;5m) which represents a manufacturing challenge, the WFE to be kept below 6μrms despite the operational temperature of 70K, and finally the mass to be kept below 300kg. The size of the Telescope has put some challenges in the manufacturing processes and the tests facilities installations. At this stage, the major critical phases which are the brazing and the grinding of the primary mirror have successfully been passed. The development and manufacturing of the Herschel Telescope is part of the Herschel Planck program funded by the European Space Agency (ESA).
Herschel is the fourth cornerstone mission in the European Space Agency (ESA) science programme. It will perform imaging photometry and spectroscopy in the far infrared and submillimetre part of the spectrum, covering approximately the 57-670 μm range. The key science objectives emphasize current questions connected to the formation of galaxies and stars, however, having unique capabilities in several ways, Herschel will be a facility available to the entire astronomical community. Herschel will be equipped with a 3.5 metre diameter passively cooled telescope. The science payload complement - two cameras/medium resolution spectrometers (PACS and SPIRE) and a very high resolution heterodyne spectrometer (HIFI) - will be housed in a superfluid helium cryostat. The ground segment will be jointly developed by the ESA, the three instrument teams, and NASA/IPAC. Herschel is scheduled to be launched into a transfer trajectory towards its operational orbit around the Earth-Sun L2 point by an Ariane 5 (shared with the ESA cosmic background mapping mission Planck) in 2007. Once operational Herschel will offer a minimum of 3 years of routine observations; roughly 2/3 of the available observing time is open to the general astronomical community through a standard competitive proposal procedure.
The `Herschel Space Observatory' (or simply `Herschel' - formerly FIRST) is the fourth Cornerstone mission in the European Space Agency (ESA) science programme. It will perform imaging photometry and spectroscopy in the far infrared and submillimetre part of the spectrum, covering approximately the 57 - 670 μm range.
The key science objectives emphasize current questions connected to the formation of galaxies and stars, however, having unique capabilities in several ways, Herschel will be a facility open for observing time proposals from the entire astronomical community. Because Herschel to some extent will be its own pathfinder, the issue of instrument calibration and data processing timescales has special importance.
Herschel will carry a 3.5 metre diameter radiatively cooled passive monolithic telescope. The science payload complement - two cameras/medium resolution spectrometers (PACS and SPIRE) and a very high resolution heterodyne spectrometer (HIFI) - will be housed in a superfluid helium cryostat. Herschel will be placed in a transfer trajectory towards its operational orbit around the Earth-Sun L2 point by an Ariane 5 (shared with the ESA cosmic background mapping mission Planck) in 2007.
Once operational Herschel will offer a minimum of 3 years of routine observations; roughly 2/3 of the available observing time is open to the general astronomical community through a competitive proposal procedure.
This paper intends to provide a selfstanding overview of the Herschel mission, and to serve as an introduction to the more specialised Herschel papers that follow in this volume.
Since ten years ASTRIUM has developed sintered Silicon Carbide (SiC) technology for space applications. Its unique thermo-mechanical properties, associated with its polishing capability, make SiC an ideal material for building ultra-stable lightweight space based telescopes or mirrors. SiC is a cost effective alternative to Beryllium and the ultra-lighweighted ULE. In Complememt to the material manufacturing process, ASTRIUM has developed several assembly techniques (bolting, brazing, bonding) for manufacturing large and complex SiC assemblies. This technology is now perfectly mature and mastered. SiC is baselined for most of the telescopes that are developed by ASTRIUM. SiC has been identified as the most suitable material for manufacturing very large crygenic telescopes. In this paper we present the development of Φ 3.5 m telescope for Herschel Mission. Herschel main goal is to study how the first stars and galaxies were formed and evolved. The Herschel Space telescope, using silicon carbide technology will be the largest space imagery telescope ever launched. The Herschel telescope will weight 300 kg rather than the 1.5 tons required with standard technology. The Herschel telescope is to be delivered in 2005 for a launch planned for 2007.
FIRST, the `Far InfraRed and Submillimeter Telescope', is the fourth cornerstone mission in the European Space Agency science program. It will perform photometry and spectroscopy in the far infrared and submillimeter part of the spectrum, covering approximately the 60 - 670 micrometers range.
The 'far IR and submillimeter telescope', (FIRST), is the fourth European Space Agency cornerstone mission in the current 'Horizons 2000' science program. FIRST will perform photometry and spectroscopy in approximately the 80-670 micrometers range in the far IR and submillimeter part of the spectrum.
FIRST and SOFIA are both future IR observatories with 3m class main mirrors having sophisticated instrumentation aboard. The present design of the FIRST imaging spectrometer PACS requires two large far-IR photoconductor arrays of 25 X 16 pixels each, the baseline material is stressed and unstressed Ge:Ga. A gallium arsenide photoconductive detector which is sensitive in the far IR (FIR) wavelength range from about 60 micrometers to 300 micrometers might offer the advantage of extending considerably the long wavelength cut- off of presently available photodetectors. FIRGA is an ESA sponsored detector development program on this matter involving international partners. The aim is a monolithic 4 X 32 demonstrator array module with associated cryogenic read-out electronics. Recent progress in material research has led to the production of Te-doped n-type GaAs layers using liquid phase epitaxy. We prepared sample detectors from those material and investigated their electrical and IR characteristics. First measurements indicate that GaAs has in principle considerable potential as a FIR photon detector. Theoretical modeling of GaAs detectors can help with the detector design and allows the prediction of response transients as a function of detector parameters. Present development activities are mainly concentration on material research, i.e. the production of GaAs:Te with improved FIR characteristics. Results of the current test and measurements are reported. The FIRGA study is intended to prepare the technology for large 2D GaAs detector arrays for far IR astronomy.
The Far InfraRed and Submillimeter Telescope (FIRST) is the last of the four Cornerstone Missions in the 'Horizon 2000' long term science plan of the European Space Agency (ESA) and as an observatory type mission it will be open to the international astronomical community. Its launch is presently foreseen for the end of 2005. The nominal mission duration will be 4.5 years and the active archive phase 3 years. Taking into account the experience from other ESA missions and in order to minimize costs, the ground segment for FIRST scientific operations will be structured in a novel 'decentralized' way, creating centers of competence.
Use of ta photoconductor array in the wavelength range from about 100 to 300 microns could add to the capability of the far-infrared imaging spectrometer in the model payload of FIRST (ESA's far-infrared and submillimeter space telescope). The GaAs detector array is a completely new development and will be included in an ESA-sponsored detector development program. The material offers the advantage of extending the wavelength range of photoconductors considerably. Essential improvement of material quality is required to bring dark current and NEP at operating temperatures around 1 K down to levels of state-of-the-art photoconductors. Recent progress has led to the production of extremely high purity GaAs layers using liquid phase epitaxy. Layers with a thickness of a few hundred microns were produced only a short time ago. They are considered good candidates to start investigations and preparation of detectors. This paper discusses recent results of the GaAs material research, detector design, and progress of array development.
We consider a 16 X 16 pixel GaAs photoconductive detector array as a new candidate for an ESA-sponsored detector development program. A photoconductor array covering the wavelength range from 150 to 300 microns can add to the capability of the far infrared imaging spectrometer in the model payload of FIRST (far infra-red and submillimeter space telescope). The GaAs detector array is a completely new development. The spectral response of GaAs has been known for years; gallium arsenide, however, was at that time not available in a quality to bring dark current and NEP at operating temperatures around 1 K down to levels of state of the art photoconductors. Recent progress in liquid phase epitaxy led to the production of very high purity GaAs. Contamination from the growth system can now be kept below the required donor concentration leading to n-type GaAs layers. Photoluminescence spectra indicate low compensation, a vital requirement for getting effective photoconductive detectors. Layers with a thickness of a few hundred microns were recently produced. The GaAs detector is likely to become available within the next few years. The paper discusses investigations of the material and first results of sampling detector development.