Space Interferometry Mission
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This article or section contains information regarding a future spaceflight. Due to the nature of the content, details may change dramatically as the launch date approaches and/or more information becomes available. |
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The Space Interferometry Mission (SIM), also called "SIM PlanetQuest," is a NASA instrument originally expected to be launched in December of 2011; however due to budget cuts it will now launch no sooner than between October 2014 and April 2015. Once in orbit, scientists expect SIM to be able to make very accurate astrometric observations of distant stars. SIM will also be a powerful general astrophysical observatory.
NASA hopes the SIM's ability to very accurately measure the distances and positions of stars will help astronomers probe for Earth-like planets in other solar systems, and possibly answer fundamental questions about the universe, such as its age and size. Additionally, SIM will measure the masses of stars, including exotic neutron stars and stellar-size black holes, plus analyze dark matter and microlensing events. It is designed to operate between 450 and 900 nm.[citation needed]
SIM works through optical interferometry. Interferometry combines light from two or more telescopes as if they were pieces of a single, gigantic telescope mirror. SIM is composed of a 9 meter boom with 1 science interferometer and 2 guide interferometers. The collecting area of each of the three instruments is 479 cm².
NASA hopes that SIM's new technology will eventually lead to the development of telescopes powerful enough to take images of Earth-like extrasolar planets orbiting distant stars and to determine whether those planets are able to sustain life — in fact, NASA has already begun developing future missions that will build on SIM's technological legacy.
SIM will make a detailed survey of approximately 100 close target stars over 5 years, and will be able to detect extrasolar planets down to 2 Earth Masses for the nearest stars. SIM will also perform a broad survey of several thousand stars improving our knowledge of the formation, evolution, and architecture of planetary systems. This broad survey will be able to detect planets of Neptune's size and larger in orbits up to 10 AU.
SIM is being developed by the Jet Propulsion Laboratory under contract with Northrop Grumman in Redondo Beach, California.[citation needed]
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[edit] The mission
SIM will operate in an Earth-trailing solar orbit. After being launched via an Evolved Expendable Launch Vehicle (EELV). SIM will slowly drift away from earth at the rate of .1 AU per year until it reaches a distance of 95 million km, this will take approximately 5.5 years. The Sun will continuously shine on the spacecraft which avoids the occultations that would occur in an Earth orbit. After achieving orbit the spacecraft's solar array and high gain antenna will be fully deployed. Systems will be checked and tracking data collected to determine the orbit achieved. The spacecraft will then take several days to disperse contaminants and eventually, after that period, will deploy all final instruments The calibration of the interferometer will take several months. It is after the calibration that "the fun begins."[1]
For the following five or so years the SIM Planetquest will perform nearly continual scientific operation. The spacecraft will be pointed using reaction wheel and small thrusters. The spacecraft's nominal viewing axis must never be with 45 degrees of the Sun or the viewing optics could suffer degradation from heating. Due to this danger pointing must be performed precisely. In addition, the velocity of spacecraft must also be precisely calculated, to within 20 mm/sec or better in order to correct for relativistic stellar aberration. Deep Space Network (DSN) ground stations will provide doppler data to ensure that the velocity is accurately calculated. Data obtained by SIM will be stored onboard the spacecraft and returned to Earth several times each week. Controllers will use special "quick turnaround" procedures to utilize SIM on any "targets of opportunity that may arise".[1]
[edit] Mission schedule
The SIM Planetquest is considered the flagship mission of the "Navigator" program. The program is, according to the 2007 Presidential Budget for NASA, "a coherent series of increasingly challenging projects, each complementary to the others and each mission building on the results and capabilities of those that preceded it as NASA searches for habitable planets outside of the solar system."[2] The program, in addition to SIM, includes the Keck Interferometer and Large Binocular Telescope Interferometer. The budget outline plans for the three during fiscal year 2007, and the plans for SIM spelled delay. The budget outlined that "SIM Phase B activity will continue while new cost and schedule plans are developed, consistent with recent funding decisions."[2] Those funding decisions included a $118.5 million cut over the FY 2006 NASA budget request in the program budget for "Navigator." during FY 2007. The budget also laid out projections for the program through the year 2010. Each year is to see successive cuts from 2006 request numbers starting with FY 2008 which promises to be around $223.9 million less for the Navigator program compared to 2006. Following years show cuts of $155.2 and $172.5 million compared to 2006 requests.[2] The budget documents reports that, a launch date of "no earlier than 2015-16, a change of approximately 3 years," is assumed in the FY 2007 budget.[2] The delays are most likely budgetary in nature, much as the FY 2007 budget actually says. The cuts in the "Navigator program are largely being absorbed by the SIM Planetquest mission. In 2006 the mission received $117 million, an increase of $8.1 million over the previous year but 2007 cuts over 2006 budget request numbers amounted to $47.9 million less for the SIM program. In 2008 $128.7 million of the $223.9 million estimated to be dropped from the Navigator budget compared to 2006 numbers will come from the SIM Planetquest mission. An addional $51.9 million less in FY 2009 and by 2010 the program should be receiving a significant amount of more funding if prediction hold true.[3]
[edit] Planet hunting
SIM Planetquest will be the most powerful extrasolar planet hunting space telescope ever built. Through the technique of interferometry the spacecraft will be able to detect planets as small as Earth.[4] SIM will perform its search for nearby Earth-like planets by looking for the "wobble" in the parent star's apparent motion as the planet orbits. SIM will accomplish this task to an accuracy of one millionth of an arcsecond, or the thickness of a nickel viewed at the distance of the Moon. Aside from searching for Earth-like planets SIM will perform what has been dubbed the "broad survey," which will look at around 2,000 stars to help determine the abundance of Neptune and larger mass planets around all star-types in this sector of the Milky Way. The planet finding doesn't stop there, however. A third part of the planet finding mission will include a search for Jupiter-mass planets around young stars. The survey will help scientists understand more about solar system formation, including the occurrence of hot Jupiters.[4] It is through the techniques pioneered by Michelson that the SIM will be able to execute its three primary planet-finding missions.
[edit] Deep Search
The Deep Search is a program intended to search for terrestrial planets (like Earth or Mars) around approximately 250 near stars. The Deep Search is the most demanding in terms of astrometric accuracy, hence the name, Deep Search. This program will use the full capability of SIM to make its accurate measurements.[5]
[edit] Broad Survey
The Broad Survey is a secondary planet search which is aims for quantity over quality. This lower accuracy program will survey a much larger 2,000 star selection. This program is aimed primarily at exploring the occurrence of Neptune and larger mass planets around stars of different types in this part of our Galaxy.[5]
[edit] Planets around young stars
SIM's third component of its planet hunting mission is the search for Jupiter mass planets around young stars. Most of the 200+ planets discovered outside of our own solar system have proven very different from the constructs in our celestial neighborhood. The discovery of Hot Jupiters has thrown planetary formation theory on its head in search of new theories to explain the formation of the burning behemoths. This portion of the planet hunt is hoping to study systems with one or more Jupiter mass planets before the system has reached a long term equilibrium.[5]
[edit] See also
[edit] Notes
- ^ a b The Mission, SIM Planetquest, Jet Propulsion Lab, NASA.
- ^ a b c d FY 2007 NASA Budget, (PDF), NASA, pg. 80-81, retrieved Nov. 2, 2006.
- ^ FY 2007 NASA Budget, (PDF), NASA, pg. 83, retrieved Nov. 2, 2006.
- ^ a b Searching for new worlds, Science Highlights, SIM Planetquest, JPL, NASA.
- ^ a b c Planet Detection, Science, SIM Planetquest, JPL.
