Space Observatories

Here is a chart of (what I hope are) all deployed and future space observatories showing their orbits, spectral bands and a graph showing spectral coverage vs. angular resolution for many of them, plus some ground based telescopes for comparison. A list with links to the mission websites is below.

On top is a schematic view of the orbits of all listed space observatories and their main spectral ranges. The markers for spectral coverage show only the spectral range for its primary instrument, many missions include a more diverse set of instruments, e.g. the Hubble telescope has a range from near infrared to near ultraviolet. See the spectrum graphic above for more detailed coverage. Solar observatories usually have a variety of instruments, covering not only electromagnetic radiation (in extreme ultraviolet, mostly) but also solar wind particles and magnetic fields, therefore they are marked as a separate category.

The chart is of course not to scale, especially the orbital planes are ordered by broad category. In reality all of these telescopes have their own orbit, but I'm trying to give a general overview here. More detailed information is available from CelesTrak. For a detailed treatment of angular resolutuion, see below.

Spectral Coverage

Not covered: Balloon telescopes and ballistic rockets, because those cover just about every wavelength above radio and generally last only a short time. The atmospheric absorption graph is shown to indicate where ground-based observations are even possible. It features absorption data from Mauna Kea/Hawaii, so it represents a best-case scenario for observation windows into space. At the low frequency end, radio waves are reflected by the ionosphere; in the sub-millimeter to near-infrared range there are a wide variety of absorption bands from atmospheric gases, mostly CO2 and water vapor (H2O); and the high frequency range above nearest ultraviolet is absorbed by Oxygen (O2) and Ozone (O3) as well as Rayleigh scattering. Only the very highest energy photons above 100 GeV are interacting with the atmosphere in a way that can be observed from the ground, this range is covered by Cherenkov telescopes.


[See also spectral range vs. resolution below.]

 

Radio & Submillimeter
RadioAstron (Spektr-R, Radio) 2011
Spektr-M (Millimetron, Microwave) 2025

Infrared
Spitzer (SST, Spitzer Space Telescope, NIR) 2003
   Spitzer Heritage Archive
NEOWISE (NEO Widefield Infrared Survey Explorer, Infrared Asteroid Search, IR) 2009-2011. Reactivated 2013
   WISE Allsky data
Nano-JASMINE (Astrometric Survey, NIR) 2017?
TESS (Transiting Exoplanet Survey Satellite, Near IR) 2017
CHEOPS (CHaracterising ExOPlanets Satellite, Opt/Near IR) 2018
   ESA science
JWST (James Webb Space Telescope, Opt/Near IR) 2018
   STScI Site - ESA site - MIRI
Euclid (Dark Energy Survey, NIR) 2020
   ESA site Small-JASMINE (Astrometric Survey, NIR) 2020
WFIRST-AFTA (Near Infrared Survey, NIR) 2025

(Near) Optical
HST (Hubble Space Telescope) (Near UV-Near IR) 1990
   ESA Hubble Site - Hubble Heritage Project - Hubble Legacy Archive - Archive Search
MOST (Microvariability and Oscillations of STars, Astroseismology) 2003
Kepler (Exoplanets & Astroseismology) 2009
NEOSSat (Near-Earth Object Surveillance Satellite) 2013
   CSA site
BRITE (6 Nanosats) 2013/14
   CanX3 - UniBRITE (CanX-3A) - BRITE Austria (CanX-3B, TUGSat-1) - BRITE-PL 1/2 - BRITE-Toronto, BRITE-Montreal
Gaia (Astrometric Survey) 2013
PLATO (Planetary Transits and Oscillations of stars) 2024

High Energy
XMM-Newton (X-ray Multi-Mirror Mission, X-ray) 1999
   ESA science
Chandra (X-ray) 1999
   HRC - ACIS - HETG - LETG 1 - LETG 2
INTEGRAL (International Gamma Ray Astrophysics Laboratory, X-ray & Gamma ray) 2002
*Swift (Gamma ray, X-ray, UV) 2004
   Italian/ASI site - UK site - PSU site - BAT - XRT - UVOT
Suzaku (Astro-EII, X-ray) 2005
AGILE (Astrorivelatore Gamma ad Immagini LEggero, X-ray & Gamma ray) 2007
*Fermi (GLAST, Gamma ray) 2008
   LAT - GBM
MAXI (Monitor of All-sky X-ray Image/ISS, X-ray) 2009
   KIBO
NuSTAR (Nuclear Spectroscopic Telescope Array, Hard X-ray) 2012
Hisaki (SPRINT-A: Spectroscopic Planet Observatory for Recognition of Interaction of Atmosphere, EUV) 2013
Astrosat (UV, X-ray) 2015
Lomonosov (Gamma Ray Bursts, Cosmic Rays) 2016
HXMT (Hard X-ray Modulation Telescope, X-ray) 2017
   UK site
Spektr-RG (SRG, Spectrum-Roentgen-Gamma, X-ray) 2017
NICER (Neutron Star Interior Composition Explorer, X-Ray timing) 2017
LATTES (X-ray transients) 2018
Spektr-UF (WSO-UV, World Space Observatory-Ultraviolet, Spektr-UF, UV) 2021
SVOM (Space-based multi-band astronomical Variable Objects Monitor, X-ray, Gamma) 2022
   Spanish site (Universidad Complutense, Madrid)
Athena+ (Advanced Telescope for High-energy Astrophysics+, X-Rays) 2028
   ESA site

Solar Observatories
WIND 1994
*SOHO (Solar & Heliospheric Observatory) 1995
   SOHO archive - ESA site - CDS - CELIAS - COSTEP - EIT - ERNE - GOLF - LASCO (de) - MDI - SUMER - SWAN (fr) - UVCS - VIRGO
ACE (Advanced Composition Explorer) 1997
RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager) 2002
GOES N, O & P (Geostationary Operational Environmental Satellite) 2006/09/10
   SXI - SWPC
Hinode (Solar-B) 2006
   EIS - SOT - XRT
*STEREO A & B (Solar Terrestrial Relations Observatory) 2006
   SECCHI - SWAVES - IMPACT - PLASTIC
PROBA-2 (PRoject for OnBoard Autonomy) 2009
   ESA science - SWAP
*SDO (Solar Dynamics Observatory) 2010
   HMI - AIA - EVE
Picard 2010
IRIS (Interface Region Imaging Spectrograph) 2013
   GSFC site
DSCOVR (Deep Space Climate Observatory) 2015
GOES R (Geostationary Operational Environmental Satellite, SXI) 2016
Aditya-1 (Solar coronagraph) 2018
DSSO (Deep Space Solar Observatory) 2018
PROBA-3 (PRoject for OnBoard Autonomy) 2019
SPP (Solar Probe Plus, Close Approach) 2018
Solar Orbiter 2018
   ESA science
Interhelio-Zond (Close Approach) 2025

Particles
PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics, on Resurs-DK1 satellite, Cosmic Rays) 2006
IBEX (Interstellar Boundary EXplorer) 2008
AMS 2 (Alpha Magnetic Spectrometer 2/ISS) 2011
CALET (CALorimetric Electron Telescope/ISS, Cosmic Rays) 2015
Wukong (DAMPE, DArk Matter Particle Explorer) 2015
Mozi (QSS, Quantum Science Satellite) 2016
JEM-EUSO (Japanese Experiment Module-Extreme Universe Space Observatory/ISS, Cosmic rays) 2018
   Italian site - Russian site

Gravity
LISA Pathfinder (Gravitational Waves) 2015
   ESA science - eLISA science
MICROSCOPE (MICRO-Satellite a traînee Compensee pour l'Observation du Principe d'Equivalence, Equivalence principle test) 2016
ACES (Atomic Clock Ensemble in Space/ISS) 2017
eLISA (Gravitational wave observatory) 2034

Passive Laser Reflectors
LAGEOS 1 & 2 (1972/1992)
LARES (Laser Relativity Satellite, Frame Dragging) 2012

Some Ground (and Air) Based Telescopes
VLA (Very Large Array, Radio Telescope Array)
LOFAR (LOw Frequency ARray)
ALMA (Atacama Large Millimeter Array, Microwave Telescope Array)
SOFIA (Stratospheric Observatory for Infrared Astronomy, Airborne IR/Microwave Telescope)
ISI (Infrared Spatial Interferometer, Mid-Infrared)
CHARA (Center for High Angular Resolution Astronomy, Optical/Near-Infrared Interferometer)
Keck (W. M. Keck Observatory, Optical/Near-Infrared Twin Interferometry Telescopes)
VLT (Very Large Telescope, Optical/Near-Infrared Quadruple Interferometry Telescopes)
GTC (Gran Telescopio de Canarias)
E-ELT (European Extremely Large Telescope, Future Optical/Near-Infrared Telescope)
MAGIC (Major Atmospheric Gamma Ray Imaging Telescope, Cherenkov Gamma-ray Telescope)
HESS (High Energy Stereoscopic System, Cherenkov Gamma-ray Telescope)
Very Long Baseline Interferometry (VLBI) Radiotelescope Arrays
EVN (The European VLBI Network)
VLBA (Very Long Baseline Array)
SKA (Square Kilometre Array)
HSA (High Sensitivity Array)
LBA (Long Baseline Array)
VERA (VLBI Exploration of Radio Astrometry)
GMVA (Global mm-VLBI Array)

* Data immediately available on the Internet

Past Missions

Akari (Infrared) 2006-2011
ASCA (X-ray) 1993-2001
Beppo-SAX (X-ray) 1996-2003
COBE (Cosmic Microwave Background) 1989-1993
Compton (Gamma Ray) 1991-2000
Copernicus (OAO-3, UV/X-ray) 1972-1981
COROT (Convection, Rotation and planetary Transits, Exoplanets & Astroseismology) 2006-2013 - French site
COS-B (Gamma Ray) 1975-1982 - ESA science
CXBN (Cosmic X-ray Background Nanosatellite, X-ray) 2012
Einstein HEAO-2 (X-ray) 1978-1992
EUVE (Extreme Ultraviolet) 1992-2001
Exosat (X-ray) 1983-1986 - ESA science
FUSE (Far Ultraviolet) 1999-2007
GALEX (Galaxy Evolution Explorer, UV) 2003-2013
Ginga (X-ray) 1987-1991
Granat (x-ray/Gamma) 1989-1998
HEAO-1 (X-ray/Gamma) 1977-1979
HEAO-3 (X-ray/Gamma) 1979-1981
Helios A/Helios B (Solar Observatory) 1974-1985 - MPG Site
Herschel (Microwave, Far Infrared) 2009-2013 - ESA science - HIFI - PACS - SPIRE
HETE 2 (X-ray) 2000-2007
Hipparcos (Optical, Astrometric Survey) 1989-1993 -
ESA science IRAS (Infrared) 1983
ISO (Infrared) 1995-1998 - ESA science
IUE (Ultraviolet) 1978-1996
Odin (Microwave & Optical) 2001-2007 (Earth obs. only after 2007)
Planck (Cosmic Microwave Background) 2009-2013
ROSAT (X-ray) 1990-1999
RXTE (Rossi X-ray Timing Explorer, X-ray) 1995
SAS-2 (Gamma Ray) 1972-1973
SAS-3 (X-ray) 1975-1979
SWAS (Submillimeter Wave) 1998-2005
TRACE (Solar Observatory) 1998-2010
UHURU (SAS-1, X-ray) 1970-1973
Ulysses (Solar Observatory, Polar Sun Orbit) 1990-2002 - ESA science - JPL site
VSOP-1 (Space-based Radio Interferometry) 1997-2005
WMAP (Wilkinson Microwave Anisotropy Probe, Cosmic Microwave Background) 2001-2010
Yohkoh (Solar Observatory) 1991-2004

Spectral Range vs. Angular Resolution

For this chart I tried to find a single measure - apart from spectral range - that characterizes remote sensing instruments across the whole spectrum. But there are many different types of instruments: cameras, spectrometers, field sensors, particle counters etc.; and many different characteristics to describe them. The most relevant one for performance is perhaps resolution, which comes in several different kinds:

  • Angular (spatial) resolution: the smallest separation at which two distinct objects can still be distinguished, measured anywhere between degrees and microarcseconds (mas). Applicable to imaging instruments that produce a two-dimensional intensity map, in the most generic definition. In combination with distance it becomes spatial resolution.
  • Spectral resolution: The minimum difference in frequency that can be distinguished, in λ/Δλ. (λ = wavelength)
  • Intensity resolution (sensitivity): The faintest source that can be distinguished from background noise. This is in principle applicable to all remote sensing instruments. It is, however, dependent on the kind of digitalization used and defined in many different ways for different sensing technologies, and therefore not easily comparable across the spectrum.
  • Temporal resolution: The shortest interval in time a change in the signal can be detected, from seconds to microseconds. This is only applicable to specific instruments used for eg. stellar seismology, finding exoplanets or gamma ray burst monitors. Or more generally recording light-curves, the change in intensity over time.
  • Polarization resolution: In degrees, also for specific instruments and with limited application.

Angular resolution seems the one best comparable across the whole spectrum, and it is also the most important for what is traditionally thought of as a "Telescope." But the trend goes toward optimizing instruments for more than one capability, like imaging spectrometers. What the future may hold can be gleaned in this entertaining article.

The given quantities in the chart show the lowest possible resolution for each instrument, except for interferometry, where more than one instrument takes part, and a very high resolution can be achieved. This is most relevant for space VLBI (SVLBI). The relevant missions are therefore represented by two lines, one for the intrinsic resolution of the instrument alone and one for the maximum resolution by VLBI with ground-based instruments.

For the low-frequency end, angular resolution is exclusively defined by the diffraction limit sin θ = 1.22 * λ/D, where θ is the minimum resolution in radians, D the aperture (diameter for spherical instruments, max. distance for interferometry) of the telescope and λ the wavelength, both in identical length units. The factor 1.22 comes from the typical diffraction pattern of concentric rings of a circular aperture and stands for the position of the first dark ring of the pattern. Note that this is a defined quantity and can vary for different optical geometries, but the results are mostly similar and so I have used this value as an approximation for all covered instruments.

Approaching the visible frequency range, the diffraction limit becomes smaller and other limits become prevalent, like the pixel-size of the imaging CCDs. For ground based instruments (and SOFIA) atmospheric disturbance is the most limiting factor, where only recently improvements like adaptive optics or lucky imaging allow interferometry to lower the diffraction limit. Space telescopes in the infrared and visible range however are always diffraction limited below a certain frequency that is determined by the properties of the imaging system.

At even higher frequencies only the imaging technology limits the resolution. In the X-ray range the most often used grazing incidence telescopes have only a small frequency dependence of their resolution, but are more sensitive to off-center angle of the source, so the given line is the best possible resolution and is mostly constant across the spectral range. At least that is how I interpret the available documentation and hope I'm right with this. In the highest frequency range, at gamma rays, imaging is achieved by tracing photon paths, similar to particle accelerators, and here again the possible resolution improves with frequency.

More

Older versions of the charts
CelesTrak Satellite orbital elements
Sky View Virtual Observatory.
NRAO National Radio Astronomy Observatory
LAMBDA Legacy Archive for Microwave Background Data
IPAC Infrared Processing and Analysis Center
STSci Space Telescope Science Institute - MAST Multimission Archive
HEASARC High Energy Astrophysics Science Archive Research Center - Observatories
Space Physics Data Facility - Heliophysics Data Portal
Goddard Projects Directory - NSSDC - Explorers
List of Space Telescopes (Wikipedia)
Earth Observation Portal
Space Weather
Space Weather Prediction Center - SDO - The Sun Now - STEREO Multistatus - ESA
Near Earth Objects
JPL NEO Program - Asteroidwatch - ESA NEO Coordination Centre - NEO Shield

1 comment :

  1. Great job. Only in L5 is Stereo B.

    Lamid

    ReplyDelete