Space Science in China

J. Jpn. Soc. Microgravity Appl. Vol. 22 No. 4 2005 (242–245)

Keynote Paper

Ji WU1 and Jin CHANG2

Abstract China started to develop space science in the early 1960s. from 1960s to 1990s we have developed some payloads for space science study onboard the spacecrafts which are not ˆxed in space science. In the 1990s the space science experiments including space astronomy have been done in the SZ spacecrafts. Up to now we have launched ˆve spacecrafts for space science experiment. Recently China's Geospace Double Star Exploration Program (DSP) is a very successful space science mission. More and more proposals, or potential projects have been proposed in recent two years. We try to brie‰y outline these new proposals, although most of them are in fact only in their conception studies.

veloped and operated during every launch activities 1. Introduction and throughout each mission lifetime cycle. China started to explore the upper atmosphere using On the theoretical part, many of the state key sounding rockets and balloons in the early 1960s. Start laboratories have been established. The scientists have from the early 70's, right after China launched its ˆrst been using observation data from both abroad and satellite DFH–1, a series of scientiˆc/experiment satel- homemade satellites. China also built up some ground lites has been launch, the so called SJ series. For exam- observation facilities, including telescope for the Sun ple SJ–1 in 1971, SJ–2 in 1984, SJ–4 in 1994 and SJ–5 observation and radars for ionosphere observations. in 1999, etc. The SJ series are mostly dedicated to In 2000, Chinese government has issued a white space environment exploration and test the radiation paper on Chinese Space Activities. In this book, space environment eŠects. A good example is SJ–5. It has its science is listed together with space technology and main goal to study the single particle event in the LEO space application and one of the three major areas of on varies circuits. Besides it also was acting as the space activities in China. Under this framework, new microgravity experiment platform carried out a space science mission proposals are called right after double-layer ‰uid science experiment, in which a re- that, for example the Double Star Program in 2001, mote science operation of this experiment was real- and also recently, for example Chang'E–1 in 2004. A ized. ground based observation chain is approved by the Since late 1980s, retrievable satellites have been em- government in 2005. It involves 15 ground stations ployed for various kinds of scientiˆc experiments, such along 120 degree east meridian line and 30 degree west as natural resource discovery by means of remote sens- latitude line. They will be given a more detailed ing and microgravity experiments. In the later experi- coverage in the following sections under the topic of ments, many satisfactory results have been achieved in ongoing projects. crystal and protein growth, cell cultivation and crop Currently, missions proposed to next ˆve years plan breeding. Innovative achievements have been scored in are intensively evaluated and selected. After the ˆrst the study of basic theory of space science. round selection, a few proposals are given higher In 1992, Chinese government initialized the manned priorities than others and got the green light to con- space program. Before the ˆrst successful manned mis- tinue for Phase A studies. These mission proposals are sion, 4 unmanned test missions have been launched Hard X-ray Modulation Telescope (HXMT) in as- from 1999 to 2002. On the missions, the scientists have tronomy, KUAFU–space storms and aurora monitor- got a lot of opportunities to carry out scientiˆc experi- ing in geospace exploration, Small Explorer for Solar ments in the ˆeld of space astronomy, space physics, Eruption (SMESE) and Space Solar Telescope (SST). space environment eŠects test, earth remote sensing, Other proposals are kept for further study and for next microgravity science including basic ‰uid physics, round of evaluation in one year, such as DMS, AS- material science and life science. TROID I, SPORT and WIMS. The details of them are Along with the manned space program, the space given in the sections under the topic of proposed environment/space weather forecast has also been de- projects.

1 Center for Space Science and Applied Research, Chinese Academy of Sciences Beijing 100080, P.R. China (E-mail: wuji＠cssar.ac.cn) 2 Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, P.R. China (E-mail: chang＠mail.pmo.ac.cn)

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– to probe the space environment in the vicinity of 2. Onging Projects the moon 2.1 Double Star Program (DSP) To accomplish the above goals, six scientiˆc pay- The Geo-space Double Star Exploration Program loads will be on board. They are, a stereo CCD camer- (DSP) is the ˆrst complete space science mission in a, a visible light band spectrometer, a laser altimeter, a China that starting from its orbit design to its payloads x-ray spectrometer, a four waveband microwave and application systems. It has been approved by the radiometer, a space environment detector package. To government on 2002 but with a early starting from mid better serve these payloads, a dedicated payload data 2001.ItisalsoajointprojectbetweenChinaandEu- management system is also employed. It composed by rope. The scientiˆc objective of DSP is to extend our a 1553B data bus controller, a 48 Gb solid state mass knowledge of the Earth's magnetosphere. It comprises memory, a power distributor and a remote data col- two Tan Ce (Explorer) spacecraft: lecting unit. The obiter is a 3-axis stabilized lunar Tan Ce 1 (TC–1) ‰ies in a highly elliptical equatorial pointing platform with capability of communicating orbit with apogee at 79000 km. Thus it will sample directly to the earth ground station and one year life- key regions on the day and night sides of the Earth time. The spacecraft including the payload is not turn- where the process of magnetic reconnection occurs. ing into its ‰y model manufacturing phase now and These reconnection processes dominate the dynam- everything shows that the planed launch date in 2007 ics of the magnetosphere. It was launched in 30 De- will be kept. cember 2003. The scientiˆc data from the payloads are mainly Tan Ce 2 (TC–2) ‰ies in a highly elliptical polar orbit received by a 50 meter antenna in Beijing (Miyun) and with apogee at 39000 km. Thus it will sample the po- backup with one 40 meter antenna in Kunming, Yun- larcapandcuspregionswhicharethemainregions nan province. There are more than one hundred scien- where energy from the Sun ‰ows into the mag- tists are awaiting for the ˆrst hand lunar exploration netosphere. Those ‰ows are largely controlled by the data coming down in 2007. reconnection processes to be studied by TC–1. It All the above is under development within the in- was successfully launched in 25 July 2004. stitutes of Chinese Academy of Sciences. Double Star provides measurements in key regions of 2.3 Meridian Project the magnetosphere. In addition, the orbits of the two The Meridian Project is a Chinese multi-station spacecraft are designed with coordination to ESA's chain along 1209E to monitor space environment, Cluster mission. Double Star and Cluster will make starting from Mohe, the most northern station in Chi- simultaneous observations when in separate but relat- na, through Beijing, Wuhan, Guangzhou and extend- ed regions. By exploiting such measurements, scien- ed to Chinese Zhongshan station in Antarctic. tists will improve their understanding of the mag- The project is composed with three systems, namely netosphere much better than from either mission a- monitoring, network and data transmission, research lone. A prime example will be when Double Star ob- and forecast. The monitoring system is further divided serves in the reconnection region on the dayside of the into four sub-systems. They are radio wave band ob- magnetosphere while Cluster observes in the so-called servation, optical observation, the Earth magnetism ``cusp'' region, where it can detect plasma ‰owing observation and sounding rocket observation. The ra- deep into the Earth's magnetosphere after entering the dio wave band observation sub-system includes the magnetosphere in the reconnection region. The two following instruments: non-coherent scattering radar, spacecrafts carry a total of sixteen scientiˆc in- MST radar, coherent scattering radar, interplanetary struments–eight from China and eight from Europe. plasma scintillation, middle wave radar and GPS The scientiˆc data are received by two ground stations receivers. The optical observation sub-system includes in Beijing (Miyun) and Shanghai (Sheshan) in China atmosphere lidar and interferometers. The Earth mag- and one ground stations in Spain (Villafranca) in Eu- netism observation sub-system includes many mag- rope. netometers. The sounding rocket sub-system will not 2.2 Chang'E–1 only carry out insitu measurement from 40 km upto Chang'E–1 is the ˆrst Chinese lunar mission. It aims 200 km, but also support the on site radar and other to launch a lunar orbiter in 2007. This mission is consi- remote sensing instrument for calibration. The sound- dered as the ˆrst step of China to go into the deep ing rocket launch site will be located in Hainan island space. The mission has four major scientiˆc objec- in south of China. tives. They are, The ground stations that will be build up or updated – to study lunar surface topography are: Mohe, Manzhouli, Harbin, Changchun, Beijing, – to analyze abundance of elements and distribu- Zhengzhou, Wuhan, Hangzhou, Hefei, Chengdu, tion of surface materials on the moon Lahsa, Shaoyang, Guangzhou, Hainan and Zhong- – to survey the global properties of the lunar shan. They form to observation chains. One is from regolith north to south along the 120E meridian line. The other

J. Jpn. Soc. Microgravity Appl. Vol. 22 No. 4 2005 ― 243 ― 51 Ji WU and Jin CHANG is from east to west along 30 degree latitude line. According to the agreement signed by the director of The project is now in detailed design phase. The Chinese space agency and the director of French space complete observation chain will be built up by 2009 for agency, France would provide the MYRIADE plat- operation. form, two instruments (LYOT and DESIR), the Con- trol and Mission Centres and a ground station. China 3. Proposed Projects would provide X and gamma ray spectrometers and 3.1 Hard X-ray Modulation Telescope (HXMT) would take in charge the Payload Data Management The HXMT mission concept consists of a slat-colli- system (including a ¿30 Gbits mass storage) and one matedhardX-raydetectorsensitivein20–250keV ground station. A launch by a DNIEPR launcher from withacollectingareaof5000cm2. Based on the recon- the Russian company KOSMOTRAS as a prime cus- struction technique by direct demodulation developed tomer is the baseline choice. in recent years, it is devoted to mainly perform a hard The raw data will be made available to the French X-ray all-sky imaging survey with both high sensitivity and Chinese scientiˆc teams through the Mission Con- and high spatial resolution. It can also make pointed trol Centre. At least two receiving ground stations are observations of certain objects in order to investigate planned for the SMESE telemetry reception, one in their spectroscopic and temporal properties in detail. France (3.4 diameter dish), one in China (11 meter The main detector of HXMT consists of 18 individual dish). The telecommands will be uploaded from a cylinder NaI(Tl)/CsI(Na) phoswich modules, each CNES station. with an area of 283.5 cm2 and a êld of view of 5.79× 3.3 Space Solar Telescope (SST) 19(FWHM). Its spatial resolution and positioning ac- The Space Solar Telescope (SST) will consist an op- curacy are 5? and 1? by using the direct demodulation tical diŠracting limited telescope with 1 M diameter, technique. The sensitivity level is 3×10－7 cm－2s－1 2–D real time polarizing spectrograph, and four small keV－1. HXMT was proposed in 1994 and selected as a attached telescopes of soft X-ray, H &alpha image project under the Major State Basic Research Program (full disk) and wide band spectrometer. The total of China in 2000 and has been listed in various space weight is about 2.0 T, eŠective power is about 1000 W. plans. It is now under construction in collaboration Sun synchronous polar circular orbit will be adopted between the Chinese Academy of Sciences and Tsin- with an orbit altitude of 800 KM; mission life is ghua University. designed to be 3–5 years. The main scientiˆc objective of HXMT is to per- The main aims of the Space Solar Telescope is to form a sensitive hard X-ray all-sky survey. In the sur- achieve a breakthrough advance in Solar Physics vey about 1000 hard X-ray sources are expected to be through coordinated, wave bandwidth coverage, high discovered, among which about half are active galactic resolution and continuously temporal evolution obser- nuclei (AGNs). This AGN sample will allow a detailed vations of transient and status in solar hydrodynamic study of the uniˆcation model of AGNs and to under- and magnetohydrodynmic processes The practical stand the composition of the cosmic hard X-ray back- contents of the scientiˆc objectives are as follows. (1) ground. Strong hard X-ray sources will be also ob- Explore the 3-dimensional structure of vector magnet- served in the pointed observation phase. We can there- ic êlds and velocity êlds with about 0.1! spatial reso- fore study their variability in the hard X-ray band with lutions by means of 2-dimensions real time polarizing unprecedented sensitivity and time resolution. spectrograph and the Stokes parameter proˆle. (2) Ex- 3.2 Small Explorer for Solar Eruptions (SMESE) plore the ˆne structures of solar atmospheres, especial- SMESE (SMall Explorer for Solar Eruptions) is a ly the heating of the chromosphere and the corona. (3) China-France joint solar mission. It will be launched Study the energy build up, storage, triggering, and around next solar maximum. Sun synchronous polar release of solar ‰ares, study the ˆne evolution of the circular orbit will be adopted with an orbit altitude of solar active region, the sunspots and the prominences. 750 km, mission life is designed to be above 3 years. (4) Study the various solar transient phenomena asso- This mission aims at the observing ‰ares and and ciated with solar terrestrial space environment, and Coronal Mass Ejections (CME) for the next solar max- provide various parameters serving the purpose of imum through a large wavelength coverage, ranging forecasts of solar activity and associated. from the gamma rays to the far-infrared. It is of prime 3.4 Dark Matter Searcher (DMS) interest for the new developing activity known as From ATIC balloon cosmic ray observation, it is Space Weather. The preliminary scientiˆc payloads shown that there is an excess around 500 GeV in the would include three instruments as follows. The electron spectrum. According to present model, the LYOTpackageismadeof3units:aLymanαcorona- dark matter particle can produce 'detectable signal' in graph, a Lymanαsolar disk imager and a Far UV disk the high resolution electron and gamma-ray spectra. imager. The DESIR (Telescope Infra-Rouge) is for DMS is a joint Chinese-Japanese project, aiming at far-infrared imaging. The HEBS includes a X-ray observing both high-energy electrons and photons, to spectrometer and a gamma ray spectrometer. ˆnd an evidence of a bump or a line in the energy spec-

52 J. Jpn. Soc. Microgravity Appl. Vol. 22 No. 4 2005 ― 244 ― Space Science in China tra of electron and gamma-ray between 10 GeV to 10 3.7 Wide Field Gamma–ray Burst Mission (WIMS) TeV. Comparing to 'CALorimetric Electron Tele- WIMS (Wide êld Imaging Multi-wavelength Spec- scope' (CALET), the size of DMS is smaller. If both trometer) will be onboard the Chinese Space Lab. It the projects can work simultaneously in the orbit, it covers the optical, soft X-ray, hard X-ray and gamma- would be very helpful to diagnose the existence of the ray energy bands. The main scientiˆc instruments of dark matter particles—WIMPS. WIMS are: (1) two wide êld optical survey telescopes 3.5 ASTROD I withdetectingareaof20cm2 each; (2) two high preci- This project has three objectives: to check the basic sion X-ray telescopes (PN–CCD detector) each with a principles of the relativity; to improve the accuracy of detecting area of 100 cm2 and energy range of 0.5–20 distance by three orders of magnitude in measuring the keV; (3) a large area X-ray telescope (proportional Sun, planets, and other minor bodies in solar system; counter) with a detecting area of 500 cm2;(4)twohard to improve the sensitivity by several times in measuring X-ray monitors (NaI/CsI phoswich detector) each the low frequency gravitational waves between 5 mHz with a detecting area of 280 cm2 andworkinthe and 5 mHz. Some key techniques are now investigat- 15–250 keV band; and (5) a hard X-ray (20–300 keV) ed. The strong international cooperation background imaging telescope (CZT detector and coded mask) is the characteristic of this project. with a detecting area of 200 cm2. The êld of view in 3.6 solar polar orbit radio telescope (SPORT) all the energy bands is 409×409. Therefore WIMS has CME is the most important solar activities to space the capability of high resolution X-ray spectroscopy weather and to the Human beings. However, many of and fast imaging for a large sky êld. the observed CMEs near the Sun by ground or near The main scientiˆc objectives of WIMS are to study earth orbit telescopes cannot eŠect us since they may the high energy bursts and to monitor the variability of go to the other side of the Sun. Therefore it is im- bright high energy sources. Speciˆcally, WIMS will portant to know where the CME's go and watch them study the following sources and phenomena: (1) the during their propagation through the interplanetary prompt emission of gamma-ray bursts at multi- space. wavelengths with zero time delay; (2) soft gamma-ray To monitor the interplanetary CME or plasma repeaters; (3) the transition of X-ray binaries between clouds by radio wave frequency that matches the den- diŠerent status; (4) X-ray bursts in neutron star X-ray sity or plasma frequency, two approaches can be binaries; (5) stellar ‰ares; and (6) the long term light taken. The ˆrst one is to listen its emission at two curves of active galactic neuclei. separate points, like a stereo, and retrieve the location Conclusion Remarks of the emission source where the plasma clouds is. The second one is to take an image of the plasma clouds Space science have been carried out in China in the with the entire inner interplanetary space at 1 AU dis- history with limited resources and eŠort but a wide tance from above the pole of the sun. The advantages êld of coverage in astronomy, space physics and ex- of the second one are: ploration, and microgravity science. In the recent Able to get an entire picture of the plasma clouds years, following the manned space program, the Dou- not only on the one that along the Sun Earth connec- ble Star Program and the Chang'E mission, space tion line science had a very fast development. According the Able to judge the total quantity of each CME event next 5 years government plan, more space science mis- from the Sun by estimate the density of the plasma sions will be approved. Therefore, China will become clouds an important space science country in the world. It is Able to forecast the space weather not only for the certainly important to have international cooperation planet Earth but also for other planet, for example during our development. Japan is one major coopera- Mars, and also for the spacecraft cruising through the tion partners to be considered in the near future. interplanetary space (Received Oct. 3, 2005)

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