Long March 2D launches TanSat carbon dioxide monitoring spacecraft

by Rui C. Barbosa

China launched its first minisatellite dedicated to the carbon dioxide detection and monitoring at 15:22 UTC on December 22 using a Long March-2D (Chang Zheng-2D) launch vehicle. Launch of TanSat occurred from the LC43/603 launch complex of the Jiuquan Satellite Launch Center.

TanSat project:

The TanSat project, funded by MOST (Ministry of Science and Technology) of China, was proposed in 2010, being officially started in January 2011. ‘Tan’ is the Chinese word for ‘Carbon’.

TanSat intended to develop a high-resolution Carbon Dioxide Spectrometer for measuring the near-infrared absorption by CO2, the development of CAPI (Cloud and Aerosol Polarimetry Imager) to compensate the CO2 measurement errors by high-resolution measurement of cloud and aerosol, to develop a spacecraft equipped with instruments capable of performing scientific observations in multiple ways as mission required, and to create of a ground segment which receives observation data and retrieves the atmosphere column-averaged CO2 dry air mole fraction (XCO2), and performs data validation by ground-based CO2 monitoring.

The main objective of the TanSat mission is to retrieve the atmosphere column-averaged CO2 dry air mole fraction with precisions of 1% (4 ppm) on national and global scales. The scientific goal of the project is to improve the understanding on the global CO2 distribution and its contribution to the climate change, and also to monitor the CO2 variation on seasonal time scales.

On board the satellite are two instruments developed at CIOMP/CAS (Changchun Institute of Optics, Fine Mechanics and Physics/Chinese Academy of Sciences), in Changchun, China.

The instruments are the CarbonSpec, a high-resolution Carbon Dioxide Spectrometer for measuring the near-infrared absorption by CO2; and the CAPI (Cloud and Aerosol Polarimetry Imager) to compensate the CO2 measurement errors by high-resolution measurement of cloud and aerosol.

The CarbonSpec is a high-resolution grating spectrometer dedicated to CO2 detection by measuring the near-infrared absorption of CO2 at 1.61 µm and at 2.06 µm, and the molecular oxygen (O2) A-band in reflected sunlight at 0.76 µm. The resolving power in the A-band is near 21,000, while that in the CO2 bands is near 12,000. The footprint size is ~2 km x 2 km and the swath is 20 km wide at nadir.

The instrument is composed of a pointing subsystem, a telescope subsystem, a beam splitter subsystem, a diffraction grating spectrometer subsystem, and an imaging subsystem.

The CAPI instrument is a wide FOV (Field of View) moderate resolution imaging spectrometer with polarization channels, used to compensate errors which are caused by clouds and aerosols based on observation in the spectral bands of ultraviolet: 0.38 µm; visible: 0.67 µm; and near infrared: 0.87, 1.375 and 1.64 µm.

Other than the cloud and aerosol detection in the various wavelength bands, CAPI is designed to obtain polarization observation data at 0.67 µm and 1.64 µm in three angles, so as to enhance the retrieval accuracy of the clouds and of aerosols.

The overall volume of TanSat is 185 x 150 x 180 (cm). Launch mass is about 500 kg (including 10 kg propellant) and its design life is 3 years. TanSat will operate in a Sun-synchronous orbit at an altitude of 700 km, and with an inclination of 98.2 degrees. The revisit period is 16 days.

The satellite platform was developed by Shanghai Institute of Microsystems and Information Technology (SIMIT), which is also responsible for the overall satellite assembly, integration and testing.

The National Satellite Meteorological Center) of CMA (China Meteorological Administration (NSMC) is responsible for the ground segment and final data products. The leading role of funding in the satellite development was taken by the Chinese Academy of Sciences (CAS). The project also has international participation with the University of Leicester and the University of Edinburgh, UK.

Launch Vehicle and Launch Site:

The Chang Zheng-2D launch vehicle is a two-stage rocket developed by the Shanghai Academy of Spaceflight Technology. With storable propellants is mainly used to launch a variety of low earth orbit satellites.

The development of CZ-2D began in February 1990. From 2002, to meet the demand of SSO satellites, the payload fairing of 3350mm in diameter and attitude control engine for second stage have been successfully developed; and the discharge of remaining propellant and de-orbit of the second stage have been realized.

This launcher is mainly used for launching LEO and SSO satellites. It is characterized with high reliability, wide application and mature technology.

The CZ-2D can launch a 1,300 kg cargo in a 645 km SSO. The rocket is 41.056m long and the first, second stages and payload fairing are all 3.35m in diameter.

Its first stage is the same of the CZ-4 Chang Zheng-4. The second stage is based on CZ-4 second stage with an improved equipment bay. Lift-off mass is 232,250 kg, total length 41,056 meters, diameter 3.35 meters and fairing length 6.983 meters. At launch it develops 2961.6kN engine thrust.

The first stage has a 27.910 meter length with a 3.35 meter diameter, consuming 183,200 kg of N2O4 / UDMH (launch mass of the first stage is 192,700 kg). Equipped with a YF-21C engine capable of a ground thrust of 2,961.6 kN and a ground specific impulse of 2,550 m/s. Burn time is 170 seconds.

The second stage has a 10.9 meter length with a 3.35 meter diameter, launch mass of 39,550 kg and consuming 45,550 kg of N2O4 / UDMH. Equipped with a YF-24C cluster engine with a main engine vacuum thrust of 742.04 kN and a vernier engine with a vacuum thrust of 47.1 kN (specific impulses of 2,942 m/s and 2,834 m/s, respectively).

The CZ-2D can use two types of fairings depending of the cargo. Type A fairing has a 2.90 meters diameter (total launch vehicle length is 37.728 meters) and Type B fairing with a diameter of 3.35 meters – total launch vehicle length is 41.056 meters.

The first launch of the CZ-2D was on August 9th, 1992 from the Jiuquan Satellite Launch Center orbiting the Fanhui Shei Weixing FSW-2-1 (22072 1992-051A) recoverable satellite.

The Jiuquan Satellite Launch Center, in Ejin-Banner – a county in Alashan League of the Inner Mongolia Autonomous Region – was the first Chinese satellite launch center and is also known as the Shuang Cheng Tze launch center.

The site includes a Technical Centre, two Launch Complexes, Mission Command and Control Centre, Launch Control Centre, propellant fuelling systems, tracking and communication systems, gas supply systems, weather forecast systems, and logistic support systems.

Jiuquan was originally used to launch scientific and recoverable satellites into medium or low earth orbits at high inclinations. It is also the place from where all the Chinese manned missions are launched. The first orbital launch took place on April 24, 1970 when the CZ-1 Chang Zheng-1 rocket launched the first Chinese satellite, the Dongfanghong-1 (04382 1970-034A).

The LC-43 launch complex, also known by South Launch Site (SLS) is equipped with two launch pads: 921 and 603. Launch pad 921 is used for the manned program for the launch of the Chang Zheng-2F launch vehicle (Shenzhou and Tiangong). The 603 launch pad is used for unmanned orbital launches by the Chang Zheng-2C, Chang Zheng-2D and Chang Zheng-4C launch vehicles.

Once the launcher stages are ready on the test and verification facility, they are transported by truck to the launch pad where they are stacked together and the fueling umbilicals are attached to the rocket. Technicians can access the different stages through the service platforms that embrace the launcher at the launch platform.

Other launch zones at the launch site are used for launching the Kuaizhou and the CZ-11 Chang Zheng-11 solid propellant launch vehicles.

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