CryoSat-2

{{See also|CryoSat-1}}

File:Antarctica 6400px from Blue Marble.jpg; CryoSat-2 is designed to study Earth's polar ice caps|alt=Satellite photograph of a large white ice cap in a dark blue ocean]]

The initial proposal for the CryoSat programme was submitted as part of a call for proposals in July 1998 for Earth Explorer missions as part of the European Space Agency's Living Planet programme.{{Cite web|url=http://www.astronautix.com/craft/cryosat.htm|title=Cryosat|last=Wade|first=Mark|publisher=Encyclopedia Astronautica|access-date=22 July 2010|archive-date=12 September 2010|archive-url=https://web.archive.org/web/20100912071812/http://www.astronautix.com/craft/cryosat.htm|url-status=dead}}{{Cite web|url=http://www.flightglobal.com/articles/2010/04/22/340602/cryosat-a-decade-long-journey-for-industry.html |title=Cryosat: a decade long journey for industry |last=Coppinger |first=Rob |date=22 April 2010 |publisher=Flight Global |access-date=22 July 2010 |archive-url=https://web.archive.org/web/20130525165350/http://www.flightglobal.com/articles/2010/04/22/340602/cryosat-a-decade-long-journey-for-industry.html |archive-date=25 May 2013 |url-status=dead }} It was selected for further studies in 1999, and following completion of a feasibility study the mission was authorised. The construction phase began in 2001, and in 2002 EADS Astrium was awarded a contract to build the spacecraft. A contract was also signed with Eurockot, to conduct the launch of the satellite using a Rokot/Briz-KM carrier rocket.

Construction of the original spacecraft was completed in August 2004. Following testing, the spacecraft was shipped to the Plesetsk Cosmodrome in Russia during August 2005 and arrived on 1 September.{{Cite web|url=http://www.eurockot.com/alist.asp?cnt=20040817&main=3 |title=L-37 |date=1 September 2005 |work=CryoSat Daily |publisher=Eurockot |access-date=22 July 2010 |url-status=dead |archive-url=https://web.archive.org/web/20060311034838/http://www.eurockot.com/alist.asp?cnt=20040817&main=3 |archive-date=11 March 2006 }} The launch occurred from Site 133/3 on 8 October; however, due to a missing command in the rocket's flight control system, the second-stage engine did not shut down at the end of its planned burn, and instead the stage burned to depletion.{{Cite web|url=http://www.russianspaceweb.com/rockot.html|title=Rockot|first=Anatoly|last=Zak|publisher=RussianSpaceWeb|access-date=22 July 2010|archive-date=26 July 2010|archive-url=https://web.archive.org/web/20100726175025/http://www.russianspaceweb.com/rockot.html|url-status=live}} This prevented the second stage and Briz-KM from separating, and as a result the rocket failed to achieve orbit. The spacecraft was lost when it reentered over the Arctic Ocean, north of Greenland.{{Cite web|url=http://www.esa.int/esaCP/SEMR3Q5Y3EE_index_0.html|title=CryoSat Mission lost due to launch failure|publisher=European Space Agency|date=8 October 2005|access-date=22 July 2010|archive-date=25 January 2010|archive-url=https://web.archive.org/web/20100125134054/http://www.esa.int/esaCP/SEMR3Q5Y3EE_index_0.html|url-status=live}}{{Cite web|url=http://www.eurockot.com/alist.asp?cnt=20040855&main=3 |title=CryoSat Mission has been lost |date=8 October 2005 |publisher=Eurockot |access-date=22 July 2010 |url-status=dead |archive-url=https://web.archive.org/web/20070927192814/http://www.eurockot.com/alist.asp?cnt=20040855&main=3 |archive-date=27 September 2007 }}

Due to the importance of the CryoSat mission for understanding global warming and reductions in polar ice caps, a replacement satellite was proposed.{{Cite web|url=http://news.bbc.co.uk/1/hi/sci/tech/4326386.stm|title=Cryosat team desperate to rebuild|date=10 October 2005|work=BBC News|access-date=22 July 2010|archive-date=23 December 2006|archive-url=https://web.archive.org/web/20061223165755/http://news.bbc.co.uk/1/hi/sci/tech/4326386.stm|url-status=live}}{{Cite web|url=http://spaceflightnow.com/news/n1004/08cryosatpreview/|title=European ice-watching satellite will launch Thursday|last=Clark|first=Stephen|date=8 April 2010|publisher=Spaceflight Now|access-date=22 July 2010|archive-date=15 July 2010|archive-url=https://web.archive.org/web/20100715024320/http://www.spaceflightnow.com/news/n1004/08cryosatpreview/|url-status=live}} The development of CryoSat-2 was authorised in February 2006, less than five months after the failure.{{Cite web|url=http://www.esa.int/esaMI/Cryosat/SEM7WFMVGJE_0.html|title=ESA confirms CryoSat recovery mission|date=24 February 2006|work=CryoSat|publisher=European Space Agency|access-date=22 July 2010|archive-date=6 March 2012|archive-url=https://web.archive.org/web/20120306145132/http://www.esa.int/esaMI/Cryosat/SEM7WFMVGJE_0.html|url-status=live}}

Like its predecessor, CryoSat-2 was constructed by EADS Astrium, with its main instrument being built by Thales Alenia Space.{{Cite web|url=http://www.esa.int/SPECIALS/Cryosat/SEM5KGFF5ZF_0.html|title=CryoSat ready for launch: Media Day at IABG/Munich|date=4 September 2009|work=CryoSat|publisher=European Space Agency|access-date=22 July 2010|archive-date=27 January 2010|archive-url=https://web.archive.org/web/20100127080258/http://www.esa.int/SPECIALS/Cryosat/SEM5KGFF5ZF_0.html|url-status=live}} Construction and testing of the spacecraft's primary instrument was completed by February 2008, when it was shipped for integration with the rest of the spacecraft.{{Cite web|url=http://www.esa.int/esaLP/SEMYSBPR4CF_LPcryosat_0.html|title=Major milestone reached in CryoSat-2 development|date=6 February 2008|work=Living Planet Programme – CryoSat-2|publisher=European Space Agency|access-date=22 July 2010|archive-date=8 November 2009|archive-url=https://web.archive.org/web/20091108053106/http://www.esa.int/esaLP/SEMYSBPR4CF_LPcryosat_0.html|url-status=live}} In August 2009, the spacecraft's ground infrastructure, which had been redesigned since the original mission, was declared ready for use.{{Cite web|url=http://www.esa.int/SPECIALS/Cryosat/SEMX9Z061YF_0.html|title=Ground segment declared ready for CryoSat mission|date=7 August 2009|work=CryoSat|publisher=European Space Agency|access-date=22 July 2010|archive-date=27 January 2010|archive-url=https://web.archive.org/web/20100127080323/http://www.esa.int/SPECIALS/Cryosat/SEMX9Z061YF_0.html|url-status=live}} Construction and testing of the spacecraft had been completed by mid-September. The Project Manager for the CryoSat-2 mission was Richard Francis, who had been the Systems Manager on the original CryoSat mission.{{Cite web|url=http://www.esa.int/esaMI/Cryosat/SEM7CFXJB5G_0_iv.html|title=CryoSat-2 Project Manager: interview with Richard Francis|date=8 February 2010|work=CryoSat|publisher=European Space Agency|access-date=22 July 2010|archive-date=2 August 2010|archive-url=https://web.archive.org/web/20100802044712/http://www.esa.int/esaMI/Cryosat/SEM7CFXJB5G_0_iv.html|url-status=live}}

CryoSat-2 is an almost-identical copy of the original spacecraft,{{Cite web|url=https://www.bbc.co.uk/blogs/thereporters/jonathanamos/2010/04/cryosat2-a-measure-of-europes.shtml|title=Cryosat-2 – A measure of Europe's ambition|last=Amos|first=Jonathan|date=9 April 2010|work=BBC News|access-date=22 July 2010|archive-date=12 April 2010|archive-url=https://web.archive.org/web/20100412094424/http://www.bbc.co.uk/blogs/thereporters/jonathanamos/2010/04/cryosat2-a-measure-of-europes.shtml|url-status=live}} however modifications were made including the addition of a backup radar altimeter.{{Cite web|url=http://www.spacenews.com/civil/cryosat-2-delay.html|archive-url=https://archive.today/20130202192121/http://www.spacenews.com/civil/cryosat-2-delay.html|url-status=dead|archive-date=2 February 2013|title=ESAs Cryosat 2 Faces Delay due to Launch Range Issues|last=de Selding|first=Peter B.|date=14 September 2009|publisher=SpaceNews.com|access-date=22 July 2010}} In total, 85 improvements were made to the spacecraft when it was rebuilt.{{Cite web|url=http://www.esa.int/esaLP/SEMAD0Q11ZE_LPcryosat_0.html|title=CryoSat-2 on the road to recovery|date=12 March 2007|work=Living Planet Programme – CryoSat-2|publisher=European Space Agency|access-date=22 July 2010|archive-date=8 November 2009|archive-url=https://web.archive.org/web/20091108052804/http://www.esa.int/esaLP/SEMAD0Q11ZE_LPcryosat_0.html|url-status=live}}

The aim of the CryoSat mission is to determine ice thickness variations on Earth's ice sheets and marine ice cover.{{Cite web |title=CryoSat Objectives - Earth Online |url=https://earth.esa.int/eogateway/missions/cryosat/objectives |access-date=2022-08-11 |website=earth.esa.int}} Its primary objective is to measure Arctic sea ice thickness, testing the hypothesis that Arctic sea ice is thinning due to climate change. Furthermore, the mission aims to monitor ice thickness changes in Antarctica and Greenland, to determine their contribution to sea level rise. The mission objectives can be summarised as:

• Determine trends in Arctic sea ice thickness
• Determine the contribution that Antarctica and Greenland are making to sea level rise
• Observe variability in Arctic and Antarctic sea ice thickness
• Observe changes in the thickness of Earth's ice caps and glaciers

CryoSat achieved its initial mission objectives following the launch of CryoSat-2, and therefore the mission was extended with new objectives.

• Assess the spatial and temporal variability of ice sheet margins, glaciers, and ice caps
• Investigate oceanic variations in the Polar regions
• Examine product contribution to operational and forecasting services
• Extend the current data record to ensure mission continuity
• Assess how snow fall and surface ice melting contribute to cryosphere meteorology
• Retrieve sea ice thickness estimates in Antarctica oceans
• Observe inland water variations

File:Cryosat2 test iabg ottobrunn.jpg

When it was approved in February 2006, the launch of CryoSat-2 was planned for March 2009. It was originally planned that like its predecessor it would be launched by a Rokot,{{Cite web |last=Krebs |first=Gunter |title=Cryosat 1,2 |url=http://space.skyrocket.de/doc_sdat/cryosat.htm |url-status=live |archive-url=https://web.archive.org/web/20100701164431/http://space.skyrocket.de/doc_sdat/cryosat.htm |archive-date=1 July 2010 |access-date=22 July 2010 |publisher=Gunter's Space Page}} however due to a lack of available launches a Dnepr rocket was selected instead. ISC Kosmotras were contracted to perform the launch.{{Cite web |last=Bergin |first=Chris |date=8 April 2010 |title=Russian Dnepr rocket launches with CryoSat-2 |url=http://www.nasaspaceflight.com/2010/04/live-dnepr-rocket-launch-cryosat-2/ |url-status=live |archive-url=https://web.archive.org/web/20100611000611/http://www.nasaspaceflight.com/2010/04/live-dnepr-rocket-launch-cryosat-2/ |archive-date=11 June 2010 |access-date=22 July 2010 |publisher=NASAspaceflight.com}} Due to delays to earlier missions and range availability problems, the launch was delayed until February 2010.{{Cite web |date=14 September 2009 |title=February launch for ESA's CryoSat ice mission |url=http://www.esa.int/SPECIALS/Cryosat/SEMZT6W0EZF_0.html |url-status=live |archive-url=https://web.archive.org/web/20100127080333/http://www.esa.int/SPECIALS/Cryosat/SEMZT6W0EZF_0.html |archive-date=27 January 2010 |access-date=22 July 2010 |work=CryoSat |publisher=European Space Agency}}

The Dnepr rocket assigned to launch CryoSat-2 arrived at the Baikonur Cosmodrome by train on 29 December 2009.{{Cite web |date=30 December 2009 |title=На Байконур доставлена ракета РС-20 |url=http://www.federalspace.ru/main.php?id=2&nid=8789 |url-status=live |archive-url=https://web.archive.org/web/20110611054737/http://www.federalspace.ru/main.php?id=2&nid=8789 |archive-date=11 June 2011 |access-date=22 July 2010 |publisher=Russian Federal Space Agency}} On 12 January 2010, the first two stages of the rocket were loaded into the launch canister, and the canister was prepared for transportation to the launch site.{{Cite web |date=12 January 2010 |title=На космодроме Байконуре начались работы по подготовке к пуску ракеты РС-20 с КА "КриоСат-2" |url=http://www.federalspace.ru/main.php?id=2&nid=8894 |url-status=live |archive-url=https://web.archive.org/web/20110611054753/http://www.federalspace.ru/main.php?id=2&nid=8894 |archive-date=11 June 2011 |access-date=22 July 2010 |publisher=Russian Federal Space Agency}} On 14 January, it was rolled out to Site 109/95, where it was installed into its silo. The next day saw the third stage transported to the silo, and installed atop the rocket.{{Cite web |date=15 January 2010 |title=На Байконуре готовятся к пуску "КриоСат-2" |url=http://www.federalspace.ru/main.php?id=2&nid=8940 |url-status=live |archive-url=https://web.archive.org/web/20110611054804/http://www.federalspace.ru/main.php?id=2&nid=8940 |archive-date=11 June 2011 |access-date=22 July 2010 |publisher=Russian Federal Space Agency}}

Following the completion of its construction, CryoSat-2 was placed into storage to await launch. In January 2010, the spacecraft was removed from storage, and shipped to Baikonur for launch. It departed Munich Franz Josef Strauss Airport aboard an Antonov An-124 aircraft on 12 January,{{Cite web |date=13 January 2010 |title=CryoSat-2 – the icy mission is hotting up |url=http://www.astrium.eads.net/en/news/cryosat-2-%E2%80%93-the-icy-mission-is-hotting-up.html |url-status=dead |archive-url=https://web.archive.org/web/20100715224154/http://www.astrium.eads.net/en/news/cryosat-2-%E2%80%93-the-icy-mission-is-hotting-up.html |archive-date=15 July 2010 |access-date=22 July 2010 |publisher=EADS Astrium}} and arrived at Baikonur the next day.{{Cite web |date=14 January 2010 |title=ESA's ice mission arrives safely at launch site |url=http://www.esa.int/SPECIALS/Cryosat/SEM1UZLJ74G_0.html |url-status=live |archive-url=https://web.archive.org/web/20100210203638/http://www.esa.int/SPECIALS/Cryosat/SEM1UZLJ74G_0.html |archive-date=10 February 2010 |access-date=22 July 2010 |work=CryoSat |publisher=European Space Agency}}{{Cite web |date=13 January 2010 |title=На космодром Байконур доставлен космический аппарат КриоСат-2 |url=http://www.federalspace.ru/main.php?id=2&nid=8916 |url-status=live |archive-url=https://web.archive.org/web/20110611054815/http://www.federalspace.ru/main.php?id=2&nid=8916 |archive-date=11 June 2011 |access-date=22 July 2010 |publisher=Russian Federal Space Agency}} Following arrival at the launch site, final assembly and testing were conducted.{{Cite web |date=12 February 2010 |title=Entry 3: Important milestone passed |url=http://www.esa.int/SPECIALS/Cryosat/SEMQDLMEG5G_0.html |url-status=live |archive-url=https://web.archive.org/web/20100502061757/http://www.esa.int/SPECIALS/Cryosat/SEMQDLMEG5G_0.html |archive-date=2 May 2010 |access-date=22 July 2010 |work=CryoSat Launch Diary |publisher=European Space Agency}}

During final testing, engineers detected that the spacecraft's X band (NATO H/I/J bands) communications antenna was transmitting only a tiny fraction of the power that it should. Thermal imaging showed that the waveguide to the antenna, deep inside the spacecraft, was very hot. Clearly that was where the missing power was being dissipated. The waveguide could not normally be inspected or repaired without major disassembly of the satellite, which would have required a return to the facilities in Europe and resulted in a major delay to the launch. To avoid doing this, a local surgeon was brought in to inspect the component with an endoscope.{{Cite web |date=29 January 2010 |title=Entry 2: CryoSat-2 undergoes surgery |url=http://www.esa.int/SPECIALS/Cryosat/SEMILKSJR4G_0.html |url-status=live |archive-url=https://web.archive.org/web/20100202083155/http://www.esa.int/SPECIALS/Cryosat/SEMILKSJR4G_0.html |archive-date=2 February 2010 |access-date=22 July 2010 |work=CryoSat Launch Diary |publisher=European Space Agency}} The surgeon, Tatiana Zykova,{{Cite web |date=29 January 2010 |title=Entry 2: CryoSat-2 undergoes surgery – images |url=http://www.esa.int/SPECIALS/Cryosat/SEMILKSJR4G_1.html |url-status=live |archive-url=https://web.archive.org/web/20100203032601/http://www.esa.int/SPECIALS/Cryosat/SEMILKSJR4G_1.html |archive-date=3 February 2010 |access-date=22 July 2010 |work=CryoSat Launch Diary |publisher=European Space Agency}} discovered that two pieces of ferrite were lodged in the tube, and was able to remove both of them. Engineers were able to assist the removal of the second one with a magnet. It was determined that the ferrite had come from an absorption load installed deep inside the antenna, which was intended to improve its performance. Some ferrite (the remaining stump of this load) was removed from inside the base of the antenna in order to prevent any further debris falling into the waveguide.

On 4 February, the CryoSat-2 spacecraft was fuelled for launch. Then on 10 February it was attached to the payload adaptor, and encapsulated in the payload fairing,{{Cite web |last1=Jäger |first1=Klaus |last2=Paul |first2=Edmund |title=Cryosat-2 Activities in February |url=http://www.astrium.eads.net/node.php?articleid=4828 |url-status=dead |archive-url=https://web.archive.org/web/20110610162427/http://www.astrium.eads.net/node.php?articleid=4828 |archive-date=10 June 2011 |access-date=22 July 2010 |publisher=EADS Astrium}} to form a unit known as the Space Head Module. This was transported to the launch pad by means of a vehicle known as the crocodile, and installed atop the carrier rocket.{{Cite web |date=16 February 2010 |title=Entry 4: Crocodile to the silo |url=http://www.esa.int/SPECIALS/Cryosat/SEMJD7NEG5G_0.html |url-status=live |archive-url=https://web.archive.org/web/20100502062413/http://www.esa.int/SPECIALS/Cryosat/SEMJD7NEG5G_0.html |archive-date=2 May 2010 |access-date=22 July 2010 |work=CryoSat Launch Diary |publisher=European Space Agency}} Rollout occurred on 15 February, and the next day the satellite was activated in order to test its systems following integration onto the rocket.

File:CryoSat-2 launch.jpg

When the spacecraft was installed atop the Dnepr, launch was scheduled to occur on 25 February, at 13:57 UTC.{{Cite web |date=11 February 2010 |title=Last look at CryoSat-2 |url=http://www.esa.int/esaEO/SEMNB5MEG5G_index_0.html |url-status=live |archive-url=https://web.archive.org/web/20100304163143/http://www.esa.int/esaEO/SEMNB5MEG5G_index_0.html |archive-date=4 March 2010 |access-date=22 July 2010 |work=Observing the Earth |publisher=European Space Agency}} Prior to this, a practice countdown was scheduled for 19 February. Several hours before the practice was scheduled to begin ISC Kosmotras announced that the launch had been delayed, and as a result the practice did not take place. The delay was caused by a concern that the second stage manoeuvring engines did not have a sufficient quantity of reserve fuel.{{Cite web |date=19 February 2010 |title=Entry 5: Launch delayed |url=http://www.esa.int/SPECIALS/Cryosat/SEMQDR7CS5G_0.html |url-status=live |archive-url=https://web.archive.org/web/20120306145632/http://www.esa.int/SPECIALS/Cryosat/SEMQDR7CS5G_0.html |archive-date=6 March 2012 |access-date=22 July 2010 |work=CryoSat Launch Diary |publisher=European Space Agency}}

Following the delay, the Space Head Module was removed from the rocket, and returned to its integration building on 22 February. Whilst it was in the integration building, daily inspections were made to ensure that the spacecraft was still functioning normally. Once the fuel issue had been resolved, the launch was rescheduled for 8 April, and launch operations resumed.{{Cite web |date=25 March 2010 |title=Entry 7: Launch campaign resumes |url=http://www.esa.int/SPECIALS/Cryosat/SEM1NT8I77G_0.html |url-status=live |archive-url=https://web.archive.org/web/20100413113402/http://www.esa.int/SPECIALS/Cryosat/SEM1NT8I77G_0.html |archive-date=13 April 2010 |access-date=22 July 2010 |work=CryoSat Launch Diary |publisher=European Space Agency}} On 1 April, the Space Head Module was returned to the silo, and reinstalled atop the Dnepr. Following integrated tests, the practice countdown was successfully conducted on 6 April.{{Cite web |last1=Jäger |first1=Klaus |last2=Paul |first2=Edmund |title=Cryosat-2 Blog, live from Kazakhstan |url=http://www.astrium.eads.net/en/articles/cryosat-the-icy-mission.html |url-status=dead |archive-url=https://web.archive.org/web/20100715111327/http://www.astrium.eads.net/en/articles/cryosat-the-icy-mission.html |archive-date=15 July 2010 |access-date=22 July 2010 |publisher=EADS Astrium}}

CryoSat-2 was launched at 13:57:04 UTC on 8 April 2010.{{Cite web |last=McDowell |first=Jonathan |title=Launch Log |url=http://planet4589.org/space/log/launchlog.txt |url-status=live |archive-url=https://web.archive.org/web/20170823205415/http://planet4589.org/space/log/launchlog.txt |archive-date=23 August 2017 |access-date=22 July 2010 |publisher=Jonathan's Space Page}} Following a successful launch,{{Cite web |last=Jones |first=Tamera |date=8 April 2010 |title=Successful launch for ESA's CryoSat-2 ice mission |url=http://planetearth.nerc.ac.uk/news/story.aspx?id=704 |url-status=dead |archive-url=https://web.archive.org/web/20120703102411/http://planetearth.nerc.ac.uk/news/story.aspx?id=704 |archive-date=3 July 2012 |access-date=22 July 2010 |publisher=Natural Environment Research Council}} CryoSat-2 separated from the upper stage of the Dnepr into a low Earth orbit. The first signals from the satellite were detected by a ground station at the Broglio Space Centre in Malindi, Kenya, seventeen minutes after launch.{{Cite web |date=8 April 2010 |title=Successful launch for ESA's CryoSat-2 ice satellite |url=https://www.esa.int/Applications/Observing_the_Earth/FutureEO/CryoSat/Successful_launch_for_ESA_s_CryoSat-2_ice_satellite |access-date=12 November 2022 |publisher=European Space Agency}}

The primary payload onboard CryoSat-2 is the SAR Interferometric Radar Altimeter (SIRAL), operating in the Ku-band (13.6 GHz).{{Cite web |title=Instruments |url=https://www.esa.int/Applications/Observing_the_Earth/FutureEO/CryoSat/Instruments |access-date=2022-08-09 |website=www.esa.int |language=en}} Unlike the original CryoSat, two SIRAL instruments are installed aboard CryoSat-2, with one serving as a backup in case the other fails. The instrument combines a pulse-limited radar altimeter and a second antenna with synthetic aperture and interferometric signal processing.{{Cite web |title=CryoSat-2 Product Handbook |url=https://earth.esa.int/eogateway/documents/20142/37627/CryoSat-Baseline-D-Product-Handbook.pdf |access-date=8 August 2022 |publisher=The European Space Agency }} SIRAL has a pulse bandwidth of 320 MHz. The instrument operates in three modes depending on the surface type being measured; low resolution mode, synthetic aperture radar (SAR) mode, and SAR interferometric (SARIn) mode. Low resolution mode is used over ice sheet interiors and oceans, SAR is used over sea ice and possible oceanographic areas, and SARIn is used around the ice sheet margins and mountain glaciers.

Low resolution mode operates in a conventional, pulse-limited mode; the area of surface seen by the instrument is limited by the length of the radar pulse transmitted by the altimeter. A single antenna transmits and receives the radar signal. This mode ensures returning echoes are uncorrelated.

The low resolution mode footprint is approximately 1.7 km. The pulse repetition frequency in this mode is 1.97 kHz.

In SAR mode, SIRAL emits a burst of 64 pulses, separated into narrow along-track beams by exploiting the Doppler Effect. Each strip is ~250 m wide, and the interval between bursts means each ground location is measured multiple times, improving accuracy.

The SAR footprint is approximately 0.31 km along-track and 1.67 km across-track.{{Cite journal |last1=Kwok |first1=R. |last2=Cunningham |first2=G. F. |date=2015-07-13 |title=Variability of Arctic sea ice thickness and volume from CryoSat-2 |journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences |volume=373 |issue=2045 |pages=20140157 |doi=10.1098/rsta.2014.0157|pmid=26032317 |bibcode=2015RSPTA.37340157K |s2cid=24724371 |doi-access=free }} The pulse repetition frequency in this mode is 18.181 kHz.

In SARIn mode, the two antennae are used to account for surface slope. The two antennae, mounted 1 m apart, receive the echo almost simultaneously. If the return signal returns from off-nadir, then it is possible to measure the angle between the baseline and echo direction, therefore estimating surface slope.

The Doppler Orbit and Radio Positioning Integration (DORIS) is the second instrument on CryoSat-2, and calculates precisely the spacecraft's orbit.{{Cite web |title=ILRS Mission Support |url=http://ilrs.gsfc.nasa.gov/satellite_missions/list_of_satellites/cryo_support.html |url-status=dead |archive-url=https://web.archive.org/web/20120306001943/http://ilrs.gsfc.nasa.gov/satellite_missions/list_of_satellites/cryo_support.html |archive-date=6 March 2012 |access-date=22 July 2010 |work=CryoSat |publisher=NASA International Laser Ranging Service}} An array of retroreflectors are also carried aboard the spacecraft, and allow measurements to be made from the ground to verify the orbital data provided by DORIS.{{Cite web |title=Cryosat |url=http://ilrs.gsfc.nasa.gov/satellite_missions/list_of_satellites/cryo_general.html |url-status=dead |archive-url=https://web.archive.org/web/20120708021314/http://ilrs.gsfc.nasa.gov/satellite_missions/list_of_satellites/cryo_general.html |archive-date=8 July 2012 |access-date=22 July 2010 |publisher=NASA International Laser Ranging Service}}

Following launch, CryoSat-2 was placed into a low Earth orbit with a perigee of {{convert|720|km}}, an apogee of {{convert|732|km}}, 92 degrees of inclination and an orbital period of 99.2 minutes.{{Cite web |title=CRYOSAT 2 Satellite details |url=http://www.n2yo.com/satellite/?s=36508 |url-status=live |archive-url=https://web.archive.org/web/20150525072246/http://www.n2yo.com/satellite/?s=36508 |archive-date=25 May 2015 |access-date=22 July 2010 |work=Real Time Satellite Tracking |publisher=N2YO.com}} It had a mass at launch of {{convert|750|kg}}, and has surpassed it's expected life of three years.

Launch and Early Orbit Phase operations were completed in the morning of 11 April 2010, and SIRAL was activated later the same day.{{Cite web |last=Amos |first=Jonathan |date=12 April 2010 |title=Esa's Cryosat mission switches on radar instrument |url=http://news.bbc.co.uk/1/hi/sci/tech/8615172.stm |access-date=22 July 2010 |work=BBC News}} At 14:40 UTC, the spacecraft returned its first scientific data.{{Cite web |date=13 April 2010 |title=ESA's ice mission delivers first data |url=http://www.esa.int/SPECIALS/Cryosat/SEMTMB9MT7G_0.html |url-status=dead |archive-url=https://web.archive.org/web/20100416164231/http://www.esa.int/SPECIALS/Cryosat/SEMTMB9MT7G_0.html |archive-date=16 April 2010 |access-date=22 July 2010 |work=CryoSat |publisher=European Space Agency}} Initial data on ice thickness was presented by the mission's Lead Investigator, Duncan Wingham, at the 2010 Living Planet Symposium on 1 July.{{Cite web |date=1 July 2010 |title=CryoSat-2 exceeding expectations |url=http://www.esa.int/SPECIALS/Cryosat/SEMBC5PZVAG_0.html |url-status=live |archive-url=https://web.archive.org/web/20120306145339/http://www.esa.int/SPECIALS/Cryosat/SEMBC5PZVAG_0.html |archive-date=6 March 2012 |access-date=22 July 2010 |work=CryoSat |publisher=European Space Agency}} Later the same month, data was made available to scientists for the first time.{{Cite web |date=20 July 2010 |title=Scientists receive first CryoSat-2 data |url=http://www.esa.int/SPECIALS/Cryosat/SEM213WNPBG_0.html |url-status=live |archive-url=https://web.archive.org/web/20100726011708/http://www.esa.int/SPECIALS/Cryosat/SEM213WNPBG_0.html |archive-date=26 July 2010 |access-date=22 July 2010 |work=CryoSat |publisher=European Space Agency}} The spacecraft underwent six months of on-orbit testing and commissioning, which concluded with a review on 22 October 2010 that found the spacecraft was operating as expected, and that it was ready to begin operations.{{cite web |last=Clark |first=Stephen |date=27 October 2010 |title=CryoSat 2 passes in-orbit tests with flying colors |url=http://www.spaceflightnow.com/news/n1010/26cryosat/ |url-status=live |archive-url=https://web.archive.org/web/20101129051541/http://spaceflightnow.com/news/n1010/26cryosat/ |archive-date=29 November 2010 |access-date=16 November 2010 |publisher=Spaceflight Now}}

The exploitation phase of the mission started on 26 October 2010 under the responsibility of Tommaso Parrinello who is currently the Mission Manager.

CryoSat successfully achieved its mission objectives following the launch of CryoSat-2.{{Cite web |title=CryoSat Objectives - Earth Online |url=https://earth.esa.int/eogateway/missions/cryosat/objectives |access-date=2022-08-11 |website=earth.esa.int}}

Sea ice thickness estimates have been produced by the Centre for Polar Observation & Modelling, the Alfred Wegener Institute (Alfred Wegener Institute for Polar and Marine Research), and NASA's Jet Propulsion Laboratory and Goddard Space Flight Center.{{Cite journal |last1=Ricker |first1=R. |last2=Hendricks |first2=S. |last3=Helm |first3=V. |last4=Skourup |first4=H. |last5=Davidson |first5=M. |date=2014-08-28 |title=Sensitivity of CryoSat-2 Arctic sea-ice freeboard and thickness on radar-waveform interpretation |url=http://www.the-cryosphere.net/8/1607/2014/tc-8-1607-2014.pdf |journal=The Cryosphere |language=English |volume=8 |issue=4 |pages=1607–1622 |doi=10.5194/tc-8-1607-2014 |bibcode=2014TCry....8.1607R |s2cid=54210240 |issn=1994-0416|doi-access=free }}{{Cite journal |last1=Kurtz |first1=N. T. |last2=Galin |first2=N. |last3=Studinger |first3=M. |date=2014-07-15 |title=An improved CryoSat-2 sea ice freeboard retrieval algorithm through the use of waveform fitting |url=https://tc.copernicus.org/articles/8/1217/2014/ |journal=The Cryosphere |language=English |volume=8 |issue=4 |pages=1217–1237 |doi=10.5194/tc-8-1217-2014 |bibcode=2014TCry....8.1217K |issn=1994-0416|doi-access=free |hdl=2060/20140017082 |hdl-access=free }} Arctic sea ice thickness data are available to view and download from the Centre for Polar Observation & Modelling.{{Cite web |title=CryoSat Operational Monitoring - Sea Ice |url=http://www.cpom.ucl.ac.uk/csopr/seaice.php |access-date=2022-08-11 |website=www.cpom.ucl.ac.uk}}

Work has been conducted to extend the sea ice thickness record to include summer (May-September). Due to the presence of melt ponds on Arctic sea ice during summer, it has been challenging to distinguish waveform returns into sea ice and sea water. In 2022, a record of Arctic summer sea ice was generated using a neural network, but it was recognised that more work must be done to resolve sources of uncertainty in the estimates.{{Cite journal |last1=Dawson |first1=Geoffrey |last2=Landy |first2=Jack |last3=Tsamados |first3=Michel |last4=Komarov |first4=Alexander S. |last5=Howell |first5=Stephen |last6=Heorton |first6=Harry |last7=Krumpen |first7=Thomas |date=2022-01-01 |title=A 10-year record of Arctic summer sea ice freeboard from CryoSat-2 |url=https://www.sciencedirect.com/science/article/pii/S0034425721004648 |journal=Remote Sensing of Environment |language=en |volume=268 |pages=112744 |doi=10.1016/j.rse.2021.112744 |bibcode=2022RSEnv.268k2744D |hdl=10037/23142 |s2cid=240242639 |issn=0034-4257|hdl-access=free }}

Data from CryoSat-2 has shown 25,000 seamounts, with more to come as data is interpreted.Amos, Jonathan. "[https://www.bbc.com/news/science-environment-29465446 Satellites detect 'thousands' of new ocean-bottom mountains] {{Webarchive|url=https://web.archive.org/web/20180421012603/http://www.bbc.com/news/science-environment-29465446 |date=21 April 2018 }}" BBC News, 2 October 2014."[https://scripps.ucsd.edu/news/new-map-exposes-previously-unseen-details-seafloor New Map Exposes Previously Unseen Details of Seafloor] {{Webarchive|url=https://web.archive.org/web/20141003183047/https://scripps.ucsd.edu/news/new-map-exposes-previously-unseen-details-seafloor |date=3 October 2014 }}"David T. Sandwell, R. Dietmar Müller, Walter H. F. Smith, Emmanuel Garcia, Richard Francis. "[https://www.science.org/doi/10.1126/science.1258213 New global marine gravity model from CryoSat-2 and Jason-1 reveals buried tectonic structure] {{Webarchive|url=https://web.archive.org/web/20141004152044/http://www.sciencemag.org/content/346/6205/65 |date=4 October 2014 }}" Science 3 October 2014: Vol. 346 no. 6205 pp. 65–67. DOI: 10.1126/science.1258213"[http://www.space.dtu.dk/english/Research/Projects/Cryosat_4Plus Cryosat 4 Plus] {{Webarchive|url=https://web.archive.org/web/20141006081535/http://www.space.dtu.dk/english/Research/Projects/Cryosat_4Plus |date=6 October 2014 }}" DTU Space

It was clear from the beginning of the CryoSat programme that an extensive series of measurements would be needed, both to understand interaction of the radar waves with the surface of the ice caps and to relate the measured freeboard of floating sea ice with its thickness. This latter, in particular, would have to take account of snow loading. For sea ice, which moves as it is blown by the wind, it was also necessary to develop techniques which could give consistent results when measured from platforms travelling at different speed (scientists on the surface, helicopter-towed sounders, aircraft-borne radars and CryoSat itself). A number of campaigns were performed under a programme called CRYOVEX which aimed to address each of the identified areas of uncertainty. These campaigns continued through the development of the original CryoSat and were planned to continue after its launch.

Following the announcement that CryoSat-2 would be built the CRYOVEX programme was extended. Experiments were conducted in Antarctica to determine how snow could affect its readings, and to provide data for calibrating the satellite.{{Cite web |date=9 August 2006 |title=Workshop on Antarctic sea-ice highlights need for CryoSat-2 mission |url=http://www.esa.int/esaLP/SEM0L7JZBQE_LPcryosat_0.html |url-status=live |archive-url=https://web.archive.org/web/20100910145118/http://www.esa.int/esaLP/SEM0L7JZBQE_LPcryosat_0.html |archive-date=10 September 2010 |access-date=22 July 2010 |work=Living Planet Programme – CryoSat-2 |publisher=European Space Agency}} In January 2007 the European Space Agency issued a request for proposals for further calibration and validation experiments.{{Cite web |date=11 January 2007 |title=CryoSat-2 Announcement of Opportunity |url=http://www.esa.int/esaLP/SEMZFRSVYVE_LPcryosat_0.html |url-status=live |archive-url=https://web.archive.org/web/20091108053111/http://www.esa.int/esaLP/SEMZFRSVYVE_LPcryosat_0.html |archive-date=8 November 2009 |access-date=22 July 2010 |work=Living Planet Programme – CryoSat-2 |publisher=European Space Agency}} Further CryoVEx experiments were conducted on Svalbard in 2007,{{Cite web |date=19 April 2007 |title=Scientists and polar explorers brave the elements in support of CryoSat-2 |url=http://www.esa.int/esaLP/SEMHIYLJC0F_LPcryosat_0.html |url-status=live |archive-url=https://web.archive.org/web/20091108013652/http://www.esa.int/esaLP/SEMHIYLJC0F_LPcryosat_0.html |archive-date=8 November 2009 |access-date=22 July 2010 |work=Living Planet Programme – CryoSat-2 |publisher=European Space Agency}} followed by a final expedition to Greenland and the Devon Ice Cap in 2008.{{Cite web |date=9 May 2008 |title=Scientists endure Arctic for last campaign prior to CryoSat-2 launch |url=http://www.esa.int/SPECIALS/Cryosat/SEMWGM2QGFF_0.html |url-status=live |archive-url=https://web.archive.org/web/20090708200206/http://www.esa.int/SPECIALS/Cryosat/SEMWGM2QGFF_0.html |archive-date=8 July 2009 |access-date=22 July 2010 |work=CryoSat |publisher=European Space Agency}} Additional snow measurements were provided by the Arctic Arc Expedition, and the Alfred Wegener Institute's Airborne Synthetic Aperture and Interferometric Radar Altimeter System (ASIRAS) instrument, mounted aboard a Dornier 228 aircraft.

{{Portal|Spaceflight}}

• ESA's Living Planet Programme
• SMOS
• GOCE
• CryoSat
• Swarm
• ADM-Aeolus
• EarthCARE
• BIOMASS
• FLEX
• ICESat (NASA)

{{Reflist|30em}}

• [http://www.esa.int/esaLP/ESAOMH1VMOC_LPcryosat_0.html CryoSat pages at ESA]
• [https://earth.esa.int/eogateway/missions/cryosat CryoSat on ESA Earth Online]
• [https://www.eoportal.org/satellite-missions/cryosat-2 CryoSat on ESA eoportal]

{{European Space Agency}}

{{Orbital launches in 2010}}

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Category:Spacecraft launched in 2010

Category:Earth observation satellites of the European Space Agency

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Category:Earth satellite radar altimeters

Category:Space synthetic aperture radar