The Wilkinson Microwave Anisotropy Probe

Completed Microwave Map of the Universe
Image Credit: NASA

Scientists announced this week that the mission of the Wilkinson Microwave Anisotropy Probe (WMAP) has been completed. The last set of observations were downloaded on 20 August 2010, and researchers are compiling the final results. The satellite was placed in a permanent parking orbit around the sun on 8 September 2010.

WMAP was launched on 30 June 2001 and placed into an orbit around SEL-2, the second Sun-Earth Lagrange point. SEL-2 lies 1,500,000 kilometers beyond the Earth on a line from the Sun to the Earth. WMAP was the first spacecraft to occupy this location. SEL-2 is extremely cold, shaded from the Sun’s activity by the Earth’s shadow and ideal as an astronomical location in space. In 2009, the Herschel Space Observatory and Planck space observatory took up residence at SEL-2. They will be joined in 2014 or 2015 by the James Webb Space Telescope.

First detected in 1964, the cosmic microwave background (CMB) radiation (television “snow” – before cable), is the remnants of the extremely hot radiation from the big-bang, now cooled to almost absolute zero after 13.73 billions years of the expansion of the universe. It is a pattern frozen in place when the cosmos was only 380,000 years old.

WMAP COBE was the successor to NASA’s Cosmic Background Explorer (COBE), which was launched on 18 November 1989 and produced the first map of the microwave radiation. Note the great increase in resolution between the COBE map at the right, and the WMAP result above.

The Planck observatory is currently making high resolution measurements of both the total intensity and polarization of the primordial CMB anisotropies that were first observed by COBE and WMAP.

The observations made by WMAP are the most accurate to date and have allowed scientists to rule out several “inflation” models about what happened in the first trillionths of a second during the birth of the cosmos, while supplying support for several other models:

  • The age of the universe is 13.73 billion years old to within 1% (0.12 billion years)
  • Ordinary matter (atoms) makes up only 4.6% of the universe (to within 0.1%)
  • Dark matter (not made up of atoms) makes up 23.3% (to within 1.3%)
  • Dark energy makes up 72.1% of the universe (to within 1.5%)

Dark energy is the force driving the galaxies in the universe apart at an ever increasing rate. At some point in the future, inhabitants of the Milky Way will not be able to see any other objects in the sky. These entities will conclude that they are at the center of the universe, and will have no information about the big bang and the creation of the cosmos as we know it today.

JWST – The James Webb Space Telescope

by Dave Fischer

James Webb Space Telescope
James Webb Space Telescope – Deployed
Credit: NASA Video

The James Webb Space Telescope (JWST) is an infrared observatory, and a partial successor to the Hubble Space Telescope. JWST does not view visible light because light from the earliest universe has shifted toward the infrared (red shift).

Infrared sensitivity is required in order to see further back in time toward the beginning of the universe than either Hubble or ground based observatories.The James Webb Space Telescope is a joint venture between NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA). In all, fifteen countries are making contributions to JWST.

The are four main components to the scientific mission:

  • Search for the first stars and galaxies that formed after the Big Bang
  • Study galaxies and their formation and evolution
  • Understand the formation of stars and planetary systems
  • Study the origins of life on planetary systems

JWST is scheduled for launch in 2014 aboard an Ariane 5 rocket. It will take up residence at the Sun-Earth Lagrange point 2 (SEL-2). SEL-2 is 1,500,000 km beyond the Earth from the Sun (the Earth-Moon L2 is only 61,500 km beyond the Moon). The location was chosen in order to be able to shield the telescope from the infrared radiation of the Sun and the Earth.

Currently, SEL-2 is occupied by the Wilkinson Microwave Anisotropy Probe (WMAP), which was launched 30 June 2001, and the Herschel and Planck observatories, which were launched together on an Ariane 5 on 14 May 2009.

The image at left is a cutaway diagram the the Ariane 5 rocket, illustrating how the JWST will fold up inside the payload fairing. With the large screen behind it, the JWST will be about 21 m in width. It will stand about three stories high. The main telescope mirror, which measures 6.5 m in diameter, is too large to launch in one piece. Instead, it consists of 17 individual mirror segments mounted on a frame which will be folded inside the fairing of the Ariane 5 at launch.

Once it arrives at SEL-2, it will unfold, as this animation shows.

There are four instruments in the Integrated Science Instrument Module designed to conduct the investigations on board the James Webb Space Telescope:

Cutaway: JWST inside Ariane 5
Image Credit: European Space Agency

Four Instruments
Image Credit: NASA

  • Mid-Infrared Instrument, or MIRI – provided by the European Consortium with the European Space Agency (ESA), and by the NASA Jet Propulsion Laboratory (JPL)
  • Near-Infrared Camera, or NIRCam – provided by the University of Arizona
  • Near-Infrared Spectrograph, or NIRSpec – provided by ESA, with components provided by NASA/GSFC.
  • Fine Guidance Sensor, or FGS – provided by the Canadian Space Agency. The FGS contains a dedicated Guider and a Tunable Filter Camera.

The image below shows the locations of the four instruments in the Integrated Science Instrument Module (ISIM). Below, the image shows the location of the instrument package within the JWST.

Image Credit: NASA

The Mid-Infrared Instrument (MIRI) is an imager/spectrograph that covers the wavelength range of 5 to 27 micrometers. The camera provides wide-field broadband imagery, and the spectrograph module provides medium-resolution spectroscopy over a smaller field of view compared to the imager. The nominal operating temperature for the MIRI is 7K. Additional information can be found at the MIRI website, Space Telescope Science Institute.

The Near Infrared Camera (NIRCam) is an imager with a large field of view and high angular resolution. The NIRCam covers a wavelength range of 0.6 to 5 micrometers. More on NIRCam.

The Near Infrared Spectrograph (NIRSpec) measures the simultaneous spectra of more than 100 objects in a 9-square-arcminute field of view. This instrument provides medium-resolution spectroscopy over a wavelength range of 1 to 5 micrometers and lower-resolution spectroscopy from 0.6 to 5 micrometers. See the Space Telescope Science Institute information on NIRSpec.

The Fine Guidance Sensor (FGS) sensor is used for both “guide star” acquisition and fine pointing. See information from the Space Telescope Science Institute about NIRSpec.

See also:

The Wikipedia article on JWST.
NASA home page for JWST.
ESA home page for JWST.
CSA home page for JWST.
Make your own Paper Model of the JWST.
YouTube and JWST.

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