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SPIRE

See also Herschel Space Observatory.

The Spectral and Photometric Imaging Receiver, is one of three scientific instruments on the European Space Agency’s Herschel Space Observatory.

Herschel Space Observatory.

Herschel Picture (Courtesy of ESA)

SPIRE logo.

The Herschel Space Observatory (HSO, or simply Herschel) was launched on 14 May 2009, and carries a 3.5 metre diameter telescope, the largest astronomical telescope ever put into space, and three scientific instruments designed to carry out imaging and spectroscopy in the 60 – 700 μm wavelength range.  This part of the spectrum is very poorly explored, as most of it is blocked by the Earth’s atmosphere, but is crucial to our understanding of star and galaxy formation and the nature and behaviour of interstellar matter.  The key science goals of Herschel are the detection and investigation of galaxies in the distant (and therefore early) universe, and the study of star formation and the interstellar medium in our own and nearby galaxies.

When carrying out observations in this part of the electromagnetic spectrum, it is important to cool the telescope and the instruments as much as possible, because warm objects are very bright in the far infrared and submillimetre.  Herschel’s telescope will be cooled to about 80 K, but its  three scientific instruments, PACS, HIFI, and SPIRE need to operate at even lower temperatures. They are therefore installed in a large helium tank or “cryostat”.  The lifetime of the cryostat in space will be at about four years, after which the helium will be used up and the instruments will become too warm to operate. 

The computer-generated picture of Herschel on the right shows the telescope mounted on top of the cryostat, both protected from direct sunlight by a large sunshade.  The spacecraft control and telemetry systems and the instrument electronics are located at the bottom under the cryostat.

SPIRE

The Cardiff AIG is the lead institute for the Herschel-SPIRE instrument, which has been built by an international consortium comprising more than 18 institutes from eight countries.  SPIRE was assembled and tested at the Rutherford Appleton Laboratory in Oxfordshire.  It has now been installed in the Herschel spacecraft and is undergoing further testing as part of the complete system prior to launch.

Camera side of the SPIRE Instrument. spectrometer side of the SPIRE Instrument.

The SPIRE instrument contains an imaging photometer (camera) and an imaging spectrometer. The camera operates in three wavelength bands centred on 250, 350 and 500 μm, and so can make images of the sky simultaneously in three submillimetre “colours”.  The spectrometer covers the range 200 – 670 μm, allowing the spectral features of atoms and molecules to be measured. 

The camera and spectrometer occupy separate compartments in the instrument box, as shown in the computer generated images left.   Each instrument compartment contains mirrors, submillimetre filters to define the wavelength bands observed, moveable mirrors to control the beam,  internal calibration sources, and detector arrays.  The detectors operate at a temperature of 0.3 K, provided by an internal cooler (located on the camera side).

The essential features of the SPIRE instrument are described in more detail in "Herschel-SPIRE: Design, Performance, and Scientific Capabilities". [305 KB]


Academics working on the equipment. Close up of the equipment.

The complete SPIRE instrument box is shown above, undergoing final check-out before delivery (top) and during installation in the Herschel cryostat with the other two instruments (below). Images courtesy of ESA.

Much more information about the Herschel mission can be found at the website of the Herschel Science Centre.

SPIRE Science

SPIRE will offer the astronomical community a powerful tool for many astrophysical studies from our own solar system to the most distant galaxies.  The instrument design has been dictated by two particular scientific programmes which Herschel is particularly suited.

Star Formation

Stars form inside clouds of gas and dust in the interstellar medium (ISM), and the very first stages of this process are not well known.  Dense regions inside such clouds may condense under their own gravity to form stars.  The stars shine brightly in the visible and ultraviolet part of the spectrum, but that radiation doesn’t escape from the cloud – it is absorbed by the dust, causing the cloud to heat up to a temperature of about 50 or 100 degrees Kelvin – not very hot  but a lot warmer than it would be without the stars inside.  Material at that temperature glows at wavelengths of about 100 μm, in the far infrared part of the spectrum – so that is where the energy comes out.  So if we want to study star formation we need to look in the far infrared.  SPIRE’s camera will allow surveys to be made of nearby interstellar clouds, observing the warm dust directly, telling us about the amount of star formation and the processes that may hinder or promote the formation of stars.

SPIRE’s high sensitivity to  dust emission also makes it the ideal instrument to study the material that is ejected in copious quantities from evolved stars, enriching the interstellar medium with heavy elements and providing the raw material for planetary systems like our own.  Studies of star formation and of the interaction of forming and evolved stars with the ISM are also, of course, intimately related to the investigation of galaxy formation and evolution, which occur through just these processes.

Galaxy Formation

Normal galaxies like the Milky Way emit about a third of their energy in the far infrared and subillimetre region due to the re-processing of stellar optical and UV radiation by interstellar dust grains.  During the periods when the galaxies formed their stars, they were actually far brighter in the far infrared than in the optical/UV due to this effect.  Galaxy formation can be viewed as star formation on a massive scale, and the study of the early stages of galaxy evolution thus requires us to detect emission from distant galaxies in the submillimetre, enabling their luminosities to be measured and their and star-forming activity to be estimated.  SPIRE will carry out surveys to detect galaxies in the process of formation in the most distant (and therefore early) Universe.   The results will tell astronomers for the first time about how and when the galaxies grew and evolved over cosmic time, and how the chemical elements of which we are made were created in the process.

The SPIRE Consortium

The SPIRE project is a large international collaboration.  Cardiff is the lead institute, with Prof. Matt Griffin as the Principal Investigator.  The Consortium includes more than 150 scientists, engineers and managers  from eight countries (Canada, China, France, Italy, Spain, Sweden, UK, USA). The following institutes have provided hardware and software elements to the instrument programme:  

Funding for SPIRE has been provided by the national agencies of the participating countries and by internal institute funding: the Canadian Space Agency (CSA); NAOC in China; Centre National d'Etudes Spatiales (CNES), Centre National de la Recherche Scientifique (CNRS), and CEA in France; Agenzia Spaziale Italiana (ASI) in Italy; Ministerio de Educacion y Ciencia (MEC) in Spain, Stockholm Observatory in Sweden; the Science and Technology Facilities Council (STFC) in the UK; and NASA in the USA.  Additional funding support for some instrument activities has been provided by ESA.

Relevant Publications

Herschel-SPIRE: design, performance, and scientific capabilities [305 KB]

Griffin, M., Abergel, A, Ade, P., André, P, Baluteau, J.-P., Bock, J., Franceschini, A., Gear, W., Glenn, J., Lellouch, E., Naylor, D., Olofsson, G., Perez-Fournon, I., Rowan-Robinson, M., Saraceno, P., Smith, A., Swinyard, B., Vigroux, L., and Wright, G.   Space Telescopes and Instrumentation I: Optical, Infrared, and Millimeter, Proceedings of the SPIE, 6265, 62650A, 2006.

The Herschel-SPIRE instrument and its capabilities for extragalactic astronomy [953 KB]

Griffin, Matthew, Abergel, Alain, Ade, Peter, André, Philippe, Baluteau, Jean-Paul, Bock, James, Franceschini, Alberto, Gear, Walter, Glenn, Jason, Griffin, Douglas, King, Ken, Lellouch, Emmanuel, Madden, Suzanne, Naylor, David, Oliver, Seb, Olofsson, Göran, Page, Mat, Perez-Fournon, Ismael, Rowan-Robinson, Michael, Saraceno, Paolo, Sawyer, Eric, Swinyard, Bruce, Vigroux, Laurent, Wright, Gillian,, and the SPIRE Consortium.  Advances in Space Research, 40, 612-619, 2007.

Contact

Prof. Matt Griffin

Telephone: +44(0)29 207 74203