The Landsat program is the longest running enterprise for acquisition of imagery of Earth from space. The first Landsat satellite was launched in 1972; the most recent, Landsat 7, was launched on April 15, 1999. The instruments on the Landsat satellites have acquired millions of images. The images, archived in the United States and at Landsat receiving stations around the world, are a unique resource for global change research and applications in agriculture, cartography, geology, forestry, regional planning, surveillance, education and national security. Landsat 7 data has eight spectral bands with spatial resolutions ranging from 15 to 60 meters.
1. History
Hughes Santa Barbara Research Center initiated design and fabrication of the first three MSS Multi-Spectral-Scanners in the same year man landed on the moon, 1969. The first prototype MSS was completed within nine months by fall of 1970 when it was tested by scanning Half Dome at Yosemite National Park.
The initial centerline for the primary layout of the MSS was drawn by Jim Kodak, the opto-mechanical design engineer who designed the Pioneer spacecraft optical camera, the first instrument to leave the solar system.
The program was called the Earth Resources Observation Satellites Program when it was initiated in 1966, but the name was changed to Landsat in 1975. In 1979, Presidential Directive 54 under President of the United States Jimmy Carter transferred Landsat operations from NASA to NOAA, recommended development of long term operational system with four additional satellites beyond Landsat 3, and recommended transition to private sector operation of Landsat. This occurred in 1985 when the Earth Observation Satellite Company (EOSAT), a partnership of Hughes Aircraft and RCA, was selected by NOAA to operate the Landsat system under a ten year contract. EOSAT operated Landsats 4 and 5, had exclusive rights to market Landsat data, and was to build Landsats 6 and 7.
In 1989, this transition had not been fully completed when NOAA's funding for the Landsat program ran out and NOAA directed that Landsats 4 and 5 be shut down, but an act of the United States Congress provided emergency funding for the rest of the year. Funding ran out again in 1990 and once again Congress provided emergency funding to NOAA for six more months of operations, requesting that agencies that used Landsat data provide the funding for the other six months of the upcoming year. The same funding problem and solution was repeated in 1991. In 1992, various efforts were made to finally procure funding for follow on Landsats and continued operations, but by the end of the year EOSAT ceased processing Landsat data. Landsat 6 was finally launched on October 5, 1993, but was lost in a launch failure. Processing of Landsat 4 and 5 data was resumed by EOSAT in 1994. NASA finally launched Landsat 7 on April 15, 1999.
The value of the Landsat program was recognized by Congress in October 1992 when it passed the Land Remote Sensing Policy Act (Public Law 102-555) authorizing the procurement of Landsat 7 and assuring the continued availability of Landsat digital data and images, at the lowest possible cost, to traditional and new users of the data.
2. Satellite chronology
Landsat 1 (originally named Earth Resources Technology Satellite 1) - launched July 23, 1972, terminated operations in 1978
Landsat 2 - launched January 22, 1975, terminated in 1981
Landsat 3 - launched March 5, 1978, terminated 1983
Landsat 4 - launched July 16, 1982, terminated 1993
Landsat 5 - launched March 1, 1984, still functioning.
Landsat 6 - launched October 5, 1993, failed to reach orbit
Landsat 7 - launched April 15, 1999, still functioning, but with faulty scan line corrector (May 2003)
3. Technical details
The Multi-Spectral-Scanner had a 9" fused silica dinner-plate mirror epoxy bonded to three invar tangent bars mounted to base of a Ni/ Au brazed Invar frame in a serreuire truss that was arranged with four "Hobbs-Links" (conceived by Dr. Gregg Hobbs) crossing at mid truss. This construct ensured the secondary mirror would simply oscillate about the primary optic axis to maintain focus despite vibration inherent from the 14-inch (360 mm) Be scan mirror. This engineering solution allowed the US to develop LANDSAT at least five years ahead of French SPOT which first used CCD arrays to stare without need for a scanner.
The MSS FPA, or Focal Plane Array consisted of 24 square optical fibers extruded down to .0002"square fiber tips in a 4x6 array to be scanned across the Nimbus spacecraft path in a +/-6 degree scan as the satellite was in a 10:30 polar orbit, hence it had to be launched from Vandenburg AFB. The fiber optic bundle was embedded in a fiber optic plate to be terminated at a relay optic device that transmitted fiber end signal on into six photodiodes and 18 photomultiplier tubes that were arrayed across a 0.30-inch (7.6 mm) thick aluminum tool plate, with sensor weight balanced vs the 9-inch (230 mm) telescope on opposite side. This main plate was assembled on a frame, then attached to the silver-loaded magnesium housing with helicoil fasteners.
Key to MSS success was the scan monitor mounted on the underbelly of the Mg housing. It consisted of a diode source & sensor mounted at ends of four flat mirrors that were tilted so that it took 14 bounces for a beam to reflect length of the three mirrors from source to sender striking Be scan mirror seven times as it reflected seven times off the flat mirrors. It only sensed three positions, both ends of scan & the mid scan, but that was all that was required to determine where MSS was pointed and electronics scanning could be calibrated to display a map.
Saturday, November 15, 2008
Thursday, November 6, 2008
Chandrayaan-1
| Chandrayaan-1 | |
|
| |
| Organization | |
| Mission type | Orbiter |
| Satellite of | |
| Launch date | 22 October 2008 from Sriharikota, India |
| Launch vehicle | PSLV-XL[1] |
| Mission duration | 2 years |
| Mass | 523 kg (1,153 lb) |
| near circular | |
| polar | |
| initial 7,500 km (4,660 mi), final 100 km (62 mi) | |
| initial 500 km (311 mi), final 100 km (62 mi) | |
Chandrayaan-1, (Sanskrit: चंद्रयान-1, lit: Moon-vehicle) is India's first mission to the moon by India's national space agency Indian Space Research Organisation (ISRO). The unmanned lunar exploration mission includes a lunar orbiter and an impactor. The spacecraft was launched by a modified version of the PSLV XL on 22 October 2008 from Satish Dhawan Space Centre, Sriharikota, Andhra Pradesh.
The remote sensing satellite weighs 1,380 kilograms (3,042 lb) at launch and 675 kilograms (1,488 lb) at lunar orbit and carries high resolution remote sensing equipment for visible, near infrared, soft and hard X-ray frequencies. Over a two-year period, it is intended to survey the lunar surface to produce a complete map of its chemical characteristics and 3-dimensional topography. The Polar Regions are of special interest, as they might contain ice.
The spacecraft was successfully launched on 22 October 2008 at 06:23 IST (00:52 UTC). The estimated cost for the project is Rs. 3.86 billion (US$ 80 million).
The mission includes five ISRO payloads and six payloads from other international space agencies including NASA, ESA, and the Bulgarian Aerospace Agency, which are being carried free of cost.
1. Objectives
The stated scientific objectives of the mission are:
- To design, develop and launch and orbit a spacecraft around the Moon using Indian made launch vehicle.
- Conduct scientific experiments using instruments on-board the spacecraft which will yield the following results:
- To prepare a three-dimensional atlas (with high spatial and altitude resolution of 5-10 m) of both near and far side of the moon.
- To conduct chemical and mineralogical mapping of the entire lunar surface for distribution of mineral and chemical elements such as Magnesium, Aluminum, Silicon, Calcium, Iron and Titanium as well as high atomic number elements such as Radon, Uranium & Thorium with high spatial resolution.
- To impact a sub-satellite ( Moon Impact Probe -MIP ) on the surface on the Moon as a fore-runner to future soft landing missions.
After full integration, the Chandrayaan-1 spacecraft (left) is seen being loaded into the Thermovac Chamber (right)
Mass
1380 kg at launch, 675 kg at lunar orbit, and 523 kg after releasing the impactor.
Dimensions
Cuboid in shape of approximately 1.5 m
Communications
X band, 0.7 m diameter parabolic antenna for payload data transmission. The Telemetry, Tracking & Command (TTC) communication operates in S band frequency.
Power
The spacecraft is mainly powered by its solar array, which includes one solar panel covering a total area of 2.15 x 1.8 m generating 700 W of power, which is stored in a 36 A·h Lithium-ion battery.[12] The spacecraft uses a bipropellant integrated propulsion system to reach lunar orbit as well as orbit and altitude maintenance while orbiting the Moon.[11]
- High-resolution mineralogical and chemical imaging of permanently shadowed north and south polar regions.
- Search for surface or sub-surface water-ice on the Moon, specially at lunar poles.
- Identification of chemical end members of lunar high land rocks.
- Chemical stratigraphy of lunar crust by remote sensing of central upland of large lunar craters, South Pole Aitken Region (SPAR) etc., where interior material may be expected.
- To map the height variation of the lunar surface features along the satellite track.
- Observation of X-ray spectrum greater than 10 keV and stereographic coverage of most of the Moon's surface with 5m resolution
- To provide new insights in understanding the Moon's origin and evolution.
Chandrayaan 1
The scientific payload has a total mass of 90 kg and contains six Indian instruments and six foreign instruments.
- The Terrain Mapping Camera (TMC) is a CCD camera with 5 m resolution and a 40 km swath in the panchromatic band and will be used to produce a high-resolution map of the Moon. The aim of this instrument is to completely map the topography of the moon. The camera works in the visible region of the electromagnetic spectrum and captures black and white stereo images. When used in conjunction with data from Lunar Laser Ranging Instrument (LLRI), it can help in better understanding of the lunar gravitational field as well. TMC is built by ISRO's Space Applications Centre (SAC) of Ahmedabad TMC was successfully tested on 29 October 2008 through a set of commands issued from ISTRAC.
- The Hyper Spectral Imager (HySI) will perform mineralogical mapping in the 400-900 nm band with a spectral resolution of 15 nm and a spatial resolution of 80 m.
- The Lunar Laser Ranging Instrument (LLRI) will determine the surface topography.
- An X-ray fluorescence spectrometer (C1XS) covering 1- 10 keV with a ground resolution of 25 km and a Solar X-ray Monitor (XSM) to detect solar flux in the 1–10 keV range.[16] C1XS will be used to map the abundance of Mg, Al, Si, Ca, Ti, and Fe at the surface, and will monitor the solar flux. This payload is a collaboration between Rutherford Appleton laboratory, U.K, ESA and ISRO.
- A High Energy X-ray/gamma ray spectrometer (HEX) for 30- 200 keV measurements with ground resolution of 40 km, the HEX will measure U, Th, 210Pb, 222Rn degassing, and other radioactive elements
- The Moon Impact Probe (MIP) developed by the ISRO, is a small satellite that will be carried by Chandrayaan-1 and will be ejected once it reaches 100 km orbit around Moon, to impact on the Moon. MIP carries three more instruments, namely, a high resolution mass spectrometer, an S-Band altimeter and a video camera. The MIP also carries with it a picture of the Indian flag, its presence marking as only the fourth nation to place a flag on the Moon after the Soviet Union, United States and Japan.
- SARA, The Sub-keV Atom Reflecting Analyser from the ESA will map composition using low energy neutral atoms sputtered from the surface.
- M3, the Moon Mineralogy Mapper from Brown University and JPL (funded by NASA) is an imaging spectrometer designed to map the surface mineral composition.
- SIR-2, A near infrared spectrometer from ESA, built at the Max Planck Institute for Solar System Research, Polish Academy of Science and University of Bergen, will also map the mineral composition using an infrared grating spectrometer. The instrument will be similar to that of the Smart-1 SIR.
- miniSAR, designed, built and tested for NASA by a large team that includes the Naval Air Warfare Center, Johns Hopkins University Applied Physics Laboratory, Sandia National Laboratories, Raytheon and Northrop Grumman; it is the active SAR system to search for lunar polar ice. The instrument will transmit right polarised radiation with a frequency of 2.5 GHz and will monitor the scattered left and right polarised radiation. The Fresnel reflectivity and the circular polarisation ratio (CPR) are the key parameters deduced from these measurements. Ice shows the Coherent Backscatter Opposition Effect which results in an enhancement of reflections and CPR, so that water content of the Moon polar region can be estimated.
- RADOM-7, Radiation Dose Monitor Experiment from the Bulgarian Academy of Sciences maps the radiation environment around the Moon.
PSLV-C11(in the picture) was used to launch Chandrayaan-1.
Chandrayaan-1 was launched on 22 October 2008 at 6.22 am IST from Satish Dhawan Space Centre using ISRO's 44.4 metre tall four-stage PSLV launch rocket. Chandrayaan will take 15 days to reach the lunar orbit. ISRO's telemetry, tracking and command network (ISTRAC) at Peenya in Bangalore, will be tracking and controlling Chandrayaan-1 over the next two years of its life span.
Since its launch, Chandrayaan has performed several engine burns, moving it into the designated geostationary transfer orbit (GTO) around earth and has successfully communicated with base center. This GTO was characterized by a 22,860 km apogee by 255 km perigee and was the initial orbit from which the five orbit raising maneuvers will be performed.
Once in GTO, Chandrayaan's on-board motor will be fired to increase its orbit around the earth. The orbit will be raised five times till it reaches 1,019 km perigee and 386,194 km apogee from the Earth on 8 November. This orbit will take the spacecraft to the vicinity of the moon. The spacecraft will rotate for about five-and-a-half days before firing the engine to slow its velocity for moon's gravity to capture it. As the spacecraft approaches the moon, its speed will be reduced to enable the gravity of the moon to capture it into an elliptical orbit. A series of engine burns will then lower its orbit to its intended 100 km circular polar orbit. Following this, the Moon Impact Probe (MIP) will be ejected from Chandrayaan-1 and all the scientific instruments/payloads are commissioned.
Chandrayaan-1 completed four orbits around the Earth, on 23 October: "The health of the spacecraft is normal and (it is) doing fine. Spinning in elliptical orbit once in every 6 hours and 30 minutes, it has completed four orbits and is in the fifth orbit."
The first orbit raising manoeuvre of Chandrayaan-1 spacecraft was performed at 09:00 hrs IST on 23 October 2008 when the spacecraft’s 440 Newton Liquid Engine was fired for about 18 minutes by commanding the spacecraft from Spacecraft Control Centre (SCC) at ISRO Telemetry, Tracking and Command Network (ISTRAC) at Peenya, Bangalore. With this engine firing, Chandrayaan-1’s apogee has been raised to 37,900 km, while its perigee has been raised a little, to 305 km. In this orbit, Chandrayaan-1 spacecraft takes about 11 hours to go round the Earth once.
The second orbit raising manoeuvre of Chandrayaan-1 spacecraft was carried out on 25 October 2008 at 05:48 IST when the spacecraft’s 440 Newton Liquid Engine was fired for about 16 minutes by commanding the spacecraft from Spacecraft Control Centre (SCC) at ISRO Telemetry, Tracking and Command Network (ISTRAC) at Peenya, Bangalore. With this engine firing, Chandrayaan-1’s apogee has been further raised to 74,715 km, while its perigee has been raised to 336 km, thus completing 20 percent of its journey. In this orbit, Chandrayaan-1 spacecraft takes about twenty-five and a half hours to go round the Earth once. This is the first time an Indian spacecraft has gone beyond the 36,000 km high geostationary orbit and reached an altitude more than twice that height.
The third orbit raising manoeuvre was initiated on 26 October 2008 at 07:08 IST. The Liquid Apogee Motor was fired for about nine and a half minutes. With this, Chandrayaan-1 entered a much higher elliptical orbit around the Earth. The apogee of this orbit lies at 164,600 km, instead of 199,277 km apogee as originally announced by the Indian Space Research Organisation (ISRO), while the perigee is at 348 km. In this orbit, Chandrayaan-1 takes about 73 hours to go round the Earth once.
The fourth orbit raising manoeuvre was carried out on October 29, 2008 at 07:38 IST. The spacecraft's liquid engine was fired for about three minutes, raising it to a more elliptical orbit whose apogee lies at 267,000 km while the perigee lies at 465 km. This makes its present orbit extends more than half the way to moon. In this orbit, the spacecraft takes about six days to go round the Earth once.
The Terrain Mapping camera (TMC) on board Chandrayaan-1 spacecraft was successfully operated on October 29, 2008 through a series of commands issued from the Spacecraft Control Centre of ISRO Telemetry, Tracking and Command Network (ISTRAC) at Bangalore.
|
The first image taken at 8:00 am IST from a height of 9,000 km shows the Northern coast of Australia. |
The second image taken at 12:30 pm from a height of 70,000 km shows Australia’s Southern Coast. |
The fifth and final orbit raising manoeuvre was carried out on November 4, 2008 04:56 am IST. The spacecraft’s liquid engine was fired for about two and a half minutes resulting in Chandrayaan-1 entering the Lunar Transfer Trajectory with an apogee of about 380,000 km.
It is projected that Chandrayaan-1 will approach the Moon on November 8, 2008. Its liquid engine will then be fired again to insert the spacecraft into lunar orbit.
The scientists considered instrumental to the success of the Chandrayaan-1 project are
- G. Madhavan Nair – Chairman, Indian Space Research Organisation
- T. K. Alex – Director, ISAC (ISRO Satellite Centre)
- Mylswamy Annadurai – Project director
- S. K. Shivkumar – Director - Telemetry, Tracking and Command Network.
- George Koshi –Mission Director
- Srinivasa Hegde – Mission Director
- M Y S Prasad – Associate Director of the Sriharikota Complex and Range Operations Director
- J N Goswami – Director of the Ahmedabad-based Physical Research Laboratory and Principal Scientific Investigator of Chandrayaan-1
- Narendra Bhandari – Head, ISRO`s Planetary Sciences and Exploration program
The ISRO is also planning a second version of Chandrayaan named Chandrayaan II. According to ISRO Chairman G. Madhavan Nair, "The Indian Space Research Organisation (ISRO) hopes to land a motorised rover on the Moon in 2009 or 2010, as a part of its second Chandrayaan mission. The rover will be designed to move on wheels on the lunar surface, pick up samples of soil or rocks, do in site chemical analysis and send the data to the mother-spacecraft Chandrayaan II, which will be orbiting above. Chandrayaan II will transmit the data to Earth."
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