TheJoint Dark Energy Mission (JDEM) was anEinstein probe that planned to focus on investigatingdark energy. JDEM was a partnership betweenNASA and theU.S. Department of Energy (DOE).
In August 2010, the Board on Physics and Astronomy of theNational Science Foundation (NSF) recommended theWide Field Infrared Survey Telescope (WFIRST) mission, a renamed JDEM-Omega proposal which has superseded SNAP, Destiny, andAdvanced Dark Energy Physics Telescope (ADEPT), as the highest priority for development in the decade around 2020. This would be a 1.5-meter telescope with a 144-megapixelHgCdTe focal plane array, located at the Sun-Earth L2Lagrange point. The expected cost is around US$1.6 billion.
The Dark Energy Space Telescope (Destiny), was a planned project byNASA andDOE, designed to perform precision measurements of theuniverse to provide an understanding ofdark energy. Thespace telescope will derive the expansion of the universe by measuring up to 3,000 distantsupernovae each year of its three-year mission lifetime, and will additionally study the structure ofmatter in the universe by measuring millions ofgalaxies in aweak gravitational lensing survey. The Destinyspacecraft features an opticaltelescope with a 1.8 metre primary mirror. The telescope imagesinfrared light onto an array of solid-state detectors. The mission is designed to be deployed in ahalo orbit about the Sun-EarthL2Lagrange point.[1]
The Destiny proposal has been superseded by theWide Field Infrared Survey Telescope (WFIRST).
The SuperNova Acceleration Probe (SNAP) mission[2] was proposed to provide an understanding of the mechanism driving theacceleration of the universe and determine the nature of dark energy. To achieve these goals, the spacecraft needed to be able to detect these supernova when they are at their brightest moment.[3] The mission was proposed as an experiment for the JDEM.[2] The satellite observatory would be capable of measuring up to 2,000 distantsupernovae each year of its three-year mission lifetime. SNAP was also planned to observe the small distortions of light from distant galaxies to reveal more about the expansion history of the universe.[4] SNAP was initially planned to launch in 2013.
To understand what is driving the acceleration of the universe, scientists need to see greaterredshifts from supernovas than what is seen from Earth. The SNAP would detect redshifts of 1.7 from distant supernovas up to 10 billion light years away. At this distance, the acceleration of the universe is easily seen. To measure the presence of dark energy, a process called weak lensing can be used.[5]
The SNAP would have used an optical setup called thethree-mirror anastigmat. This consists of a main mirror with a diameter of 2 meters to take in light. It reflects this light to a second mirror. Then this light is transferred to two additional smaller mirrors which direct the light to the spacecraft's instruments. It will also contain 72 different cameras. 36 of them are able to detectvisible light and the other 36 detectinfrared light. Its cameras combined produces the equivalence of a 600 megapixel camera. The resolution of the camera is about 0.2 arcseconds in the visible spectrum and 0.3 arcseconds in the infrared spectrum. The SNAP would also have a spectrograph attached to it. The purpose of it is to detect what type of supernova SNAP is observing, determine the redshift, detect changes between different supernovas, and store supernova spectra for future reference.[6]
JDEM recognized several potential problems of the SNAP project:
The SNAP proposal has been superseded by theWide Field Infrared Survey Telescope (WFIRST).
This article incorporates text from this source, which is in thepublic domain. This article incorporates text from this source, which is in thepublic domain. This article incorporates text from this source, which is in thepublic domain. This article incorporates text from this source, which is in thepublic domain. This article incorporates text from this source, which is in thepublic domain.| Operating |
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