CryoSat
Encyclopedia
CryoSat is an ESA
programme which will monitor variations in the extent and thickness of polar ice through use of a satellite
in low Earth orbit
. The information provided about the behaviour of coastal glaciers that drain thinning ice sheets will be key to better predictions of future sea-level rise. The CryoSat-1
spacecraft was lost in a launch failure in 2005, however the programme was resumed with the successful launch of a replacement, CryoSat-2
, launched on 8 April 2010.
CryoSat is operated from the European Space Operations Centre
(ESOC) in Darmstadt, Germany.
/ Interferometric
Radar
Altimeter
). SIRAL operates in one of three modes, depending on where (above the Earth's surface) CryoSat was flying. Over the oceans and ice sheet interiors, CryoSat operates like a traditional radar altimeter. Over sea ice, coherently transmitted echoes are combined (synthetic aperture
processing) to reduce the surface footprint so that CryoSat could map smaller ice floes. CryoSat's most advanced mode is used around the ice sheet margins and over mountain glaciers. Here, the altimeter performs synthetic aperture processing and uses a second antenna as an interferometer to determine the across-track angle to the earliest radar return. This provides the exact surface location being measured when the surface is sloping.
The original CryoSat was proposed in 1998 by Duncan Wingham
of University College London
. The satellite's planned three year mission was to survey natural and human driven changes in the cryosphere
on Earth. It was designed to provide much more accurate data on the rate of change of the surface elevation of the polar ice sheet
s and sea ice
thickness. It was the first ESA Earth Sciences satellite selected through open, scientific competition. It was destroyed on launch October 8, 2005. The existing satellite is therefore CryoSat-2, but the mission is still known as simply CryoSat.
Although largely the same as the original satellite a number of key improvements were included in CryoSat-2. The most significant was the decision to provide a fully duplicated payload to enable the mission to continue if a fault caused the loss of the SIRAL radar, but there were many other changes "under the hood". Some of these were caused by obsolescence in the original design, some improved reliability and others made the satellite easier to operate. Despite all the changes the mission remains the same and the performance, in terms of measurement capability and accuracy, remains the same. , the launch was scheduled for February 25, 2010 with a Dnepr rocket from the Baikonur Cosmodrome
, but this was delayed. The CryoSat 2 launched on April 8, 2010 at 13:57 UTC.
For positioning purposes, CryoSat included a DORIS
receiver, a laser
retroreflector
and three star trackers.
The ERS-1
and ERS-2
satellites were precursors that tested the techniques used by CryoSat.
in Russia
on October 8, 2005, using a Rockot
launcher. (Rockot is a modified SS-19 rocket which was originally an ICBM
designed to deliver nuclear weapons, but which Russia is now eliminating in accordance with the START
treaties.) According to Mr. Yuri Bakhvalov, First Deputy Director General of the Khrunichev Space Centre
, when the automatic command to switch off the second stage engine did not take effect, the second stage continued to operate until it ran out of fuel and as a consequence the planned separation of the third (Breeze-KM) stage of the rocket which carried the CryoSat satellite did not take place, and would thus have remained attached to the second stage. The upper rocket stages, together with the satellite, probably crashed in the Lincoln Sea
.
Analysis of the error revealed that it was caused by faults in the programming of the rocket, which had not been detected in simulations.
After the launch failure of CryoSat, ESA immediately started to plan a replacement CryoSat mission. This included securing the industrial team which had built the original, ordering parts which have a long delivery time and establishing a funding scheme within existing budgets. Due to the importance of the scientific goals of this satellite, there was enormous support for this, and the initial phases for CryoSat-2 were approved when ESA's Earth Observation Programme Board agreed to build a copy of the spacecraft on February 23, 2006.
European Space Agency
The European Space Agency , established in 1975, is an intergovernmental organisation dedicated to the exploration of space, currently with 18 member states...
programme which will monitor variations in the extent and thickness of polar ice through use of a satellite
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
in low Earth orbit
Low Earth orbit
A low Earth orbit is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km...
. The information provided about the behaviour of coastal glaciers that drain thinning ice sheets will be key to better predictions of future sea-level rise. The CryoSat-1
CryoSat-1
CryoSat-1, also known as just CryoSat, was a European Space Agency satellite which was lost in a launch failure in 2005. It was to have been operated as part of the CryoSat programme to study the Earth's polar ice caps....
spacecraft was lost in a launch failure in 2005, however the programme was resumed with the successful launch of a replacement, CryoSat-2
CryoSat-2
CryoSat-2 is a European Space Agency environmental research satellite which was launched in April 2010. It provides scientists with data about the polar ice caps and tracks changes in the thickness of the ice with a resolution of about . This information is useful for monitoring climate change...
, launched on 8 April 2010.
CryoSat is operated from the European Space Operations Centre
European Space Operations Centre
The European Space Operations Centre is responsible for controlling ESA satellites and space probes. The centre is located in Darmstadt, Germany. It is Mission Control for most of the space projects of the ESA. Since its creation in 1967, the centre has operated 60 European space missions...
(ESOC) in Darmstadt, Germany.
Description
CryoSat's primary instrument is SIRAL (SARSynthetic aperture radar
Synthetic-aperture radar is a form of radar whose defining characteristic is its use of relative motion between an antenna and its target region to provide distinctive long-term coherent-signal variations that are exploited to obtain finer spatial resolution than is possible with conventional...
/ Interferometric
Interferometry
Interferometry refers to a family of techniques in which electromagnetic waves are superimposed in order to extract information about the waves. An instrument used to interfere waves is called an interferometer. Interferometry is an important investigative technique in the fields of astronomy,...
Radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
Altimeter
Altimeter
An altimeter is an instrument used to measure the altitude of an object above a fixed level. The measurement of altitude is called altimetry, which is related to the term bathymetry, the measurement of depth underwater.-Pressure altimeter:...
). SIRAL operates in one of three modes, depending on where (above the Earth's surface) CryoSat was flying. Over the oceans and ice sheet interiors, CryoSat operates like a traditional radar altimeter. Over sea ice, coherently transmitted echoes are combined (synthetic aperture
Synthetic aperture radar
Synthetic-aperture radar is a form of radar whose defining characteristic is its use of relative motion between an antenna and its target region to provide distinctive long-term coherent-signal variations that are exploited to obtain finer spatial resolution than is possible with conventional...
processing) to reduce the surface footprint so that CryoSat could map smaller ice floes. CryoSat's most advanced mode is used around the ice sheet margins and over mountain glaciers. Here, the altimeter performs synthetic aperture processing and uses a second antenna as an interferometer to determine the across-track angle to the earliest radar return. This provides the exact surface location being measured when the surface is sloping.
The original CryoSat was proposed in 1998 by Duncan Wingham
Duncan Wingham
Duncan Wingham is Professor of Climate Physics at University College London, and was the first Director of the Centre for Polar Observation & Modelling. He is a member of the NERC Science and Technology Board and is Principal Scientist for the CryoSat Satellite Mission.In the 90s, Wingham was...
of University College London
University College London
University College London is a public research university located in London, United Kingdom and the oldest and largest constituent college of the federal University of London...
. The satellite's planned three year mission was to survey natural and human driven changes in the cryosphere
Cryosphere
The cryosphere is the term which collectively describes the portions of the Earth’s surface where water is in solid form, including sea ice, lake ice, river ice, snow cover, glaciers, ice caps and ice sheets, and frozen ground . Thus there is a wide overlap with the hydrosphere...
on Earth. It was designed to provide much more accurate data on the rate of change of the surface elevation of the polar ice sheet
Ice sheet
An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² , thus also known as continental glacier...
s and sea ice
Sea ice
Sea ice is largely formed from seawater that freezes. Because the oceans consist of saltwater, this occurs below the freezing point of pure water, at about -1.8 °C ....
thickness. It was the first ESA Earth Sciences satellite selected through open, scientific competition. It was destroyed on launch October 8, 2005. The existing satellite is therefore CryoSat-2, but the mission is still known as simply CryoSat.
Although largely the same as the original satellite a number of key improvements were included in CryoSat-2. The most significant was the decision to provide a fully duplicated payload to enable the mission to continue if a fault caused the loss of the SIRAL radar, but there were many other changes "under the hood". Some of these were caused by obsolescence in the original design, some improved reliability and others made the satellite easier to operate. Despite all the changes the mission remains the same and the performance, in terms of measurement capability and accuracy, remains the same. , the launch was scheduled for February 25, 2010 with a Dnepr rocket from the Baikonur Cosmodrome
Baikonur Cosmodrome
The Baikonur Cosmodrome , also called Tyuratam, is the world's first and largest operational space launch facility. It is located in the desert steppe of Kazakhstan, about east of the Aral Sea, north of the Syr Darya river, near Tyuratam railway station, at 90 meters above sea level...
, but this was delayed. The CryoSat 2 launched on April 8, 2010 at 13:57 UTC.
For positioning purposes, CryoSat included a DORIS
DORIS (geodesy)
Doppler Orbitography and Radiopositioning Integrated by Satellite is a French satellite system used for the determination of satellite orbits and for positioning.-Principle:...
receiver, a laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
retroreflector
Retroreflector
A retroreflector is a device or surface that reflects light back to its source with a minimum scattering of light. An electromagnetic wave front is reflected back along a vector that is parallel to but opposite in direction from the wave's source. The device or surface's angle of incidence is...
and three star trackers.
The ERS-1
European Remote-Sensing Satellite
European remote sensing satellite was the European Space Agency's first Earth-observing satellite. It was launched on July 17, 1991 into a Sun-synchronous polar orbit at a height of 782–785 km.-Instruments:...
and ERS-2
European Remote-Sensing Satellite
European remote sensing satellite was the European Space Agency's first Earth-observing satellite. It was launched on July 17, 1991 into a Sun-synchronous polar orbit at a height of 782–785 km.-Instruments:...
satellites were precursors that tested the techniques used by CryoSat.
Launch failure of original cryosat
CryoSat was launched from the Plesetsk CosmodromePlesetsk Cosmodrome
Plesetsk Cosmodrome is a Russian spaceport, located in Arkhangelsk Oblast, about 800 km north of Moscow and approximately 200 km south of Arkhangelsk.-Overview:...
in Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
on October 8, 2005, using a Rockot
Rockot
The Rokot , also transliterated as a the pun Rockot, is a Russian space launch vehicle that can launch a payload of 1,950 kilograms into a 200 kilometre high Earth orbit with 63° inclination. It is a derivative of the UR-100N intercontinental ballistic missile , supplied and operated by Eurockot...
launcher. (Rockot is a modified SS-19 rocket which was originally an ICBM
Intercontinental ballistic missile
An intercontinental ballistic missile is a ballistic missile with a long range typically designed for nuclear weapons delivery...
designed to deliver nuclear weapons, but which Russia is now eliminating in accordance with the START
START II
START II was a bilateral treaty between the United States of America and Russia on the Reduction and Limitation of Strategic Offensive Arms. It was signed by United States President George H. W...
treaties.) According to Mr. Yuri Bakhvalov, First Deputy Director General of the Khrunichev Space Centre
Khrunichev
Khrunichev State Research and Production Space Center is a Moscow-based producer of spacecraft and space-launch systems, including the Proton and Rokot rockets. The company's history dates back to 1916, when an automobile factory was established outside Moscow...
, when the automatic command to switch off the second stage engine did not take effect, the second stage continued to operate until it ran out of fuel and as a consequence the planned separation of the third (Breeze-KM) stage of the rocket which carried the CryoSat satellite did not take place, and would thus have remained attached to the second stage. The upper rocket stages, together with the satellite, probably crashed in the Lincoln Sea
Lincoln Sea
Lincoln Sea is a body of water in the Arctic Ocean, stretching from Cape Columbia, Canada, in the west to Cape Morris Jesup, Greenland, in the east. The northern limit is defined as the great circle line between those two headlands. It is covered with sea ice throughout the year, the thickest sea...
.
Analysis of the error revealed that it was caused by faults in the programming of the rocket, which had not been detected in simulations.
After the launch failure of CryoSat, ESA immediately started to plan a replacement CryoSat mission. This included securing the industrial team which had built the original, ordering parts which have a long delivery time and establishing a funding scheme within existing budgets. Due to the importance of the scientific goals of this satellite, there was enormous support for this, and the initial phases for CryoSat-2 were approved when ESA's Earth Observation Programme Board agreed to build a copy of the spacecraft on February 23, 2006.
See also
- Gravity Recovery and Climate ExperimentGravity Recovery and Climate ExperimentThe Gravity Recovery And Climate Experiment , a joint mission of NASA and the German Space Agency, has been making detailed measurements of Earth's gravity field since its launch in March 2002....
(GRACE) NASA - launch 2002 - ICESatICESatICESat , part of NASA's Earth Observing System, was a satellite mission for measuring ice sheet mass balance, cloud and aerosol heights, as well as land topography and vegetation characteristics...
NASA - launch 2003
- Soil Moisture and Ocean Salinity satelliteSoil Moisture and Ocean Salinity satelliteThe Soil Moisture and Ocean Salinity Satellite is a part of ESA's Living Planet Programme intended to provide new insights into Earth's water cycle and climate...
(SMOS) ESA - launch 2009 - Gravity Field and Steady-State Ocean Circulation ExplorerGravity Field and Steady-State Ocean Circulation ExplorerThe Gravity Field and Steady-State Ocean Circulation Explorer is an ESA satellite that was launched on March 17, 2009. It is a satellite carrying a highly sensitive gravity gradiometer which detects fine density differences in the crust and oceans of the Earth.GOCE data will have many uses,...
(GOCE) ESA - launch 2009 - Atmospheric Dynamics Mission - Aeolus (ADM-Aeolus) ESA - launch 2010
External links
- Cryosat rocket fault laid bare
- CryoSat pages at ESA
- CryoSat-2 page at ESA Spacecraft Operations
- "Ice mission almost set for launch" – By Helen Briggs, BBC News, 22 July 2005
- Why did Cryosat crash? Australian Broadcasting Company's The Lab Cryosat story
- Cryosat-2: Scientists and Polar Explorers Collect Vital Support Data.
- Nature article The salt flat with curious curves says "the salt flat is also being used for EnvisatEnvisatEnvisat is an Earth-observing satellite. It was launched on 1 March 2002 aboard an Ariane 5 from the Guyana Space Centre in Kourou, French Guyana into a Sun synchronous polar orbit at an altitude of...
, a European satellite, and could be used to calibrate future orbiters such as Cryosat-2"