LONG BASELINE STELLAR INTERFEROMETERS

Operational Ground-Based Interferometers

The following interferometers have ceased operations - the indicated dates are approximately the dates that the interferometers were operational:
A Timeline of Stellar Interferometry from 1955 to 2000 shows the development of these interferometers.

Ground-Based Interferometers and Instruments under Construction

Ground-Based Interferometry Projects Under Development

Balloon Interferometry

Wallops Flight Facility | Columbia Scientific Balloon Facility | StratoCat | JAXA | KISS Exoplanet 2009
  • FITE Far-Infrared Interferometric Telescope Experiment (Nagoya University, Japan).
  • BETTII, Balloon Experimental Twin Telescope for Infrared Interferometry (Goddard Space Flight Center).

Space Interferometry at NASA

The role of interferometry in space science, and in particular in the search for exoplanets, is explained at JPL'sPlanet Quest webpage. The interferometry missions that NASA had been planning have all been slowded down, deferred, or cancelled. Several interferometry mission concepts were developed as part of NASA's Exoplanet Exploration Program. The 2010 Decadal Survey New Worlds, New Horizons in Astronomy and Astrophysicsrecommended further technology development for the 2010-2020 decade, but recommended against continuing development of the Space Interferometry Mission.

The Space Interferometry Mission was designed as a 6 m baseline fixed structure for planet-finding through narrow-angle astrometry. SIM has now been cancelled. It had had its origins in the Bahcall Report of 1991. SIM was in Phase B of mission development when in 2006 it was converted to a technology program. All the technology for SIM was completed. SIM was not recommended by the 2010 Decadal Survey and consequently NASA requested in September 2010 that its development be halted.

The Terrestrial Planet Finder Interferometer was a concept for a formation flying interferometer to search for Earth-like planets around nearby stars. TPF-I was being developed as a possible collaboration with ESA's Darwinmission for launched sometime around 2020. The Astronomy and Astrophysics Survey for 2000-2010,Astronomy and Astrophysics in the New Millenium endorse technology development for TPF leading to a possible interferometry mission in the 2010-2010 decade. Now, although TPF no longer exists as a planned mission within NASA, some technology work continues. Efforts in 2009 and 2010 have included broadband nulling with theAdaptive Nuller and demonstrations with the Planet Detection Testbed. The 2010 Decadal Survey recommended a continuation of technology development for starlight suppression under the title of "New Worlds Technology Development Program," leading to a mission early in the 2020-2030 decade.

The Space Infrared Interferometric Telescope (SPIRIT) was studied as a candidate NASA "Origins Probe" mission. SPIRIT is a far-infrared (25 - 400 microns) spatio-spectral interferometer that provides angular resolution 0.3*(lambda/100 microns) arcsec and simultaneous R > 3000 spectral resolution (i.e., integral field spectroscopic) observations in a 1 arcmin instantaneous field of view, with ~10 micro-Jy continuum and ~10-19 W m-2 spectral line sensitivity across its entire spectral range. SPIRIT was designed to image protoplanetary disks and measure the distributions of water vapor and ice to learn how the conditions for habitability arise during the planet formation process; image structures in a large number of debris disks to find and characterize unseen exoplanets; and make profound contributions to our understanding of the formation, merger history, and star formation history of galaxies. The European counterpart to SPIRIT is called FIRIT, the Far-Infrared Interferometric Telescope.

The NASA Astrophysics Roadmap Committee recognized the need for space interferometry to address a wide variety of science questions in its July 2013 report to the NASA Astrophysics Subcommittee.

NASA Research Announcements relevant to the Exoplanet Exploration Program can be found at the Research Opportunities home page. NASA Research Opportunities are solicited through the NSPIRES website. Various NASA Email Updates for the press and media are also available.

For those seeking more information about the politics of NASA science NASA Watch is an excellent (unofficial) resource.

Space Interferometry at ESA

The European Space Agency's involvement with space interferometry would be through its Cosmic Vision, a long-range plan which describes possible missions in the period 2015-2025. Information on the missions can be found at the ESA Space Science Homepage and through the ESA Bulletin. Information about ESA's technology planning can be found at the SRE-PA website. Email notification of news from ESA is available by subscription. The ESA websites for their Industry Portal, Invitations to Tender, and General Studies Program list opportunities for related contracts.
The Darwin mission was proposed in 2007 as a concept for Phase A Study within ESA's Cosmic Vision, which includes missions beyond 2015. It was not chosen for further study, and will no doubt be re-proposed during the next round in 2010. In 2008-2009 ESA is seeking advice for future planet finding missions through its Exoplanet Roadmap Advisory Team which should produce a draft report in January 2010.
Related work in formation flying in Europe is ongoing. The Proba-3 mission will be a formation flying technology demonstrator funded by ESA. It will fly RF and optical metrology and use cold-gas and electrical micro-propulsion thrusters. Proba-3 had been a XEUS precursor, but XEUS has become IXO and is no longer a formation flying mission. The Swedish Space Agency will launch their Prisma mission between November 2009 and February 2010 with a Darwin metrology breadboard. Orbital Satellite Services is a company in Sweden that promises to extend the life of geostationary satellites by docking with them and reprovisioning them, as will be demonstrated in the SMART OLEV mission. The French space agency (CNES) had been studying Simbol-X as a possible X-ray formation flying mission in collaboration with the Italian space agency, but after the Italians withdrew support in late 2008, budget constraints forced the CNES to cancel the mission in April 2009.
  • GENIE - Nulling interferometry with the VLTI. Nulling at 3.6 and/or 10 microns. Work on GENIE ceased in late 2006.
  • COROT - transit survey.

Interferometry Projects Being Studied

  • DAViNCI - Visible Nulling Coronagraph
  • OVLA - Optical Very Large Array (LISE, Obs. Haute Provence, France).
  • SI - Stellar Imager (Goddard Space Flight Center, NASA).
  • Large-Aperture Mirror Array - LAMA
  • MAXIM a space-based X-Ray Interferometer.
  • SPECS Submillimeter Probe of the Evolution of Cosmic Structure (concept originated at Goddard Space Flight Center, NASA; studied as a NASA "vision mission" at Goddard and JPL under leadership of Dr. Martin Harwit/Cornell) (and also this link, though it is behind a paywall)
  • SPIRIT - Space Infrared Inferferometric Telescope, studied as an Origins Probe mission (study led by Goddard Space Flight Center, NASA).
  • OSIRIS - Astrometric interferometer which was proposed to be attached to the Space Station in 2003 (Institute of Astronomy, Russia).
  • FIRI - Far-Infrared Interferometer mission concept, in response to the ESA L-class Call for White Papers
The development of DIVA, the Deutsches Interferometer fur Vielkanalphotometrie und Astrometrie, was halted in November 2002 and the mission was cancelled due to financial problems in early 2003 (AIP, Germany).
The University of Puerto Rico Interferometer, Fenton Hill Observatory, New Mexico, ceased development in late 2001.

Interferometry Related Groups and Institutions

Interferometry Related Pages

Interferometry with single telescopes

Please note that some of the links previously contained on this page (links to tutorial material in particular) have been moved to the Introduction page of OLBIN.

Selected Astronomical Resources

Formation Flying Links

Darwin and TPF-I are mission concepts that have been considered at NASA and ESA. Currently neither is in development. Darwin and TPF-I will require formation flying technology to control the relative positions of satellites that are several tens to several hundred meters apart with a resolution of several centimeters or tens of centimeters. The following notes describe missions with related technology.
The term formation flying is also applied to what might be termed constellations where the separation is roughly 100 km or more, and the resolution is only at the kilometer level. Examples of this include missions such as the two satellites that comprise GRACE, and the Earth-observing "A-train" constellation which includes Cloudsat andCalipso. Also the four microsatellites of the Essaim technology demonstrator, although described as a formation, are each several hundred kilometers apart. The four satellites of ESA's Cluster mission are another example, although this constellation has an orbit with a larger eccentricity. Future constellation missions include Swarm, to be launched about 2010.
Closer formation flying in Earth-orbit, with separations of tens of kilometers or even less than 2 km, is being planned for TanDEM-X. TanDEM-X is an Earth-observing synthetic aperture radar designed as an upgrade to the TerraSAR-X mission and having a proposed launch date in late 2009.
Autonomous Rendezvous and Docking missions are a separate, but also active area of research. The entirely autonomous NASA DART mission ended prematurely with a mishap in 2004. However, the DARPA Orbital Express mission was a tremendous success. Orbital Satellite Services is a company in Sweden that promises to extend the life of satellites by docking with them and reprovisioning them, as will be demonstrated in theSMART OLEV (Orbital Life Extension Vehicle) mission. A launch near 2012 is anticipated.
DARPA is currently sponsoring futher work related to Formation Flying, which involves fractionated spacecraft.
The AFRL co-sponsors the University Nanosatellite Program. The winner of the Nanosat-3 competition was the University of Texas at Austin, whose FASTRAC satellites will test aspects of close formation flying.
CubeSat developed by California Polytechnic State University, San Luis Obispo and Stanford University's Space Systems Development Lab. The CubeSat program creates launch opportunities for universities previously unable to access space. Neither NASA nor ESA are currently funding research in formation flying that is directly applicable to Darwin or TPF-I. It is also true that neither NASA nor ESA have a formation flying mission in their strategic plans other than these two missions. [In 2008 XEUS (ESA) was combined with Con-X (NASA) to form IXO, the International X-ray Observatory.]
DARPA and AFRL Projects
Research Teams, Ground-based Testbeds, and other links

CubeSat Links

The Generic Nanosatellite Bus was developed for the BRITE missions to enable a 20x20x20 cm satellite with 1 arcminute pointing. Examples that use the bus (due for launch in 2011) include the following:
Also likely scheduled for launch in the near-term are the following:
CanX-4 & CanX-5

CubeSats are smaller, being no more than 10x10x10 cm and weighing no more than 1.3 kg, and packaged for launch in a P-POD. Of additional interest are the CubeSat developers workshops, and the AIAA Small Sat andESA 4S conference series. Clyde Space specializes in providing CubeSat systems. The NASA Small Satellite Missions provides access to space for small mission concepts. NASA has contracted with CalPoly for P-POD services. The NASA Office of the Chief Technologist is actively promoting innovation in space technology through the use of small satellites.

Software Links

Hardware Links

Aerospace Companies

The following companies have ties or interests in the space interferometry projects of NASA or ESA:
Alcatel Alenia Space (France), Alenia Aerospazio (Italy), Ball Aerospace (US), Dutch Space (NL), Lockheed Martin (US), Astrium (France), TNO TPD (The Netherlands), TRW (US).

The sites that I would most recommend for a visit are the A.A. Michelson links, the Mnt Wilson Virtual Tour, theVirtual Radio Interferometer, and the Origins Web Site.
This page is slowly expanding as I find new items of interest. I update the page periodically. Meetings of theGrantchester Institute have proved useful. Fabien Malbet introduced me to Web Secretary, which is an absolutely marvelous Perl Script for tracking changes to web pages. I keep track of preprints and newly published paers this way.