Beijing Astronomical Observatory

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The Astronomical Observatory Beijing ( Chinese  北京天文臺  /  北京天文台 , Pinyin Běijīng Tiānwéntái ) in the district Chaoyang , Datun Road 20a, was an astronomical research institution of the Chinese Academy of Sciences , which in April 2001 in the National Astronomical Observatories opened. Due to the urbanization of the former Chaoyang district, astronomical observation is no longer possible on Datun Street. Today the headquarters of the National Astronomical Observatories of the Chinese Academy of Sciences are located there.

history

Since the 580er years ago, at the beginning of the Sui Dynasty , there was in the Imperial Palace Library (祕書省, Pinyin Bìshūshěng ) a Astrological Office (太史曹, Pinyin Tàishǐcáo ), in addition to compiling the calendar and the supervision of the water meter (the palace guards changed every two hours) also carried out astronomical observations. Renamed several times, the authority, still subordinate to the palace library, was named "Bureau for Astronomy" (司 天臺, Pinyin Sītiāntái ) from 758 . In 1267, at the invitation of Kublai Khan, the Persian astronomer Jamal ad-Din came to Beijing and brought modern astronomical instruments with him. Thereupon the office for astronomy was taken out of the apparatus of the palace library and as "office for astronomy" (司天監, Pinyin Sītiānjiān ) an independent authority within the imperial government. The tasks of the Office for Astronomy were, in addition to the annual publication of the official calendar, mainly to carry out astronomical observations and to keep records about them, as well as to train astronomy students.

In 1279 the astronomers Guo Shoujing and Wang Xun had an observation tower built from rammed earth, a good 2 km southeast of the imperial palace , just outside the Yuan-era city ​​wall, which was clad with fired bricks on the outside. The Persian observation devices were set up on the platform. In 1370, in the 3rd year of the Ming Dynasty , the Astronomy Office was renamed the “ Imperial Astronomical Office ” and in 1442 the “ Old Beijing Observatory ” was built on the site of the original observation tower. New instruments were added, but in principle the tower remained in operation until 1926. After the Xinhai Revolution of 1911 and the fall of the Qing Dynasty , the observatory was renamed the "Central Observatory" (中央 觀 像 臺, Pinyin Zhōngyāng Guānxiàngtái ) and placed under the Ministry of Education in 1912 . In 1921, a three-story building was added to the northeast corner of the tower, which now served as an observatory. From 1929, however, only meteorological observations were carried out there; the tower became a museum. State-funded astronomy - the Shanghai Astronomical Observatory was still operated by Jesuits at the time - now took place under the umbrella of the Institute for Astronomy of the Academia Sinica, founded in 1928, in the observatory on the Purple Mountain near Nanjing .

After the founding of the People's Republic of China, the Chinese Academy of Sciences began building a modern observatory in Beijing from 1958, initially the main office in Datun-Str. 20a on the northern outskirts, not far from Peking University and Tsinghua University , then branch offices, so-called “observation bases” (观测 基地, Pinyin Guāncè Jīdì ) in Xinglong , Huairou , Miyun , Shahe and Wuqing .

Miyun Observatory

After its foundation, the Beijing Astronomical Observatory primarily dealt with solar observations, initially with optical instruments. In 1964, however, people began to think about a radio observatory, and in December of that year the choice for a location fell on the then Bulaotun People's Commune in Miyun County , about 80 km northeast of the main administration at the foot of the Yan Mountains . After drawing up detailed plans, the Academy of Sciences approved on October 8, 1966, completely unaffected by the Cultural Revolution that broke out in May of that year , the Beijing astronomers' request to set up a radio-astronomical observation station there. In 1967 the station was ready for use. 16 antennas, each 9 m in diameter, each equipped with a receiver for 146 MHz, stood exactly in an east-west direction, 72 m apart, and thus formed an interferometer with a variable baseline length from 72 m to 1080 m. With this system (today's "antenna group A") one began to observe type I radio flashes triggered by solar flares and the accompanying magnetic storms , which interfered with the functioning of radar systems, among other things.

Cassiopeia A

In 1974 antenna group A was supplemented by a further row of 16 antennas oriented in a north-south direction. All antennas in the system were now equipped with receivers for 450 MHz, and in the early 1980s with receivers for 232 MHz. After a few difficulties, it was possible to interconnect the antennas to form a large virtual telescope with a synthetic aperture , known internationally as the Miyun Synthesis Radio Telescope or MSRT. On December 26, 1983, it was possible to take a two-dimensional image of the radio source Cassiopeia A (a supernova remnant). Around 1985 the system was converted to the current arrangement, with the original 16 antennas in the middle and 6 antennas to the left and right of it, also 9 m in diameter and 12 m apart - the so-called "antenna group B". The operating frequency of the system is still 232 MHz, with a bandwidth of 1.5 MHz. Since May 1998 the MSRT has been used again for daily solar observations; its sensitivity is 0.003 solar flux units and the resolution is 3.8 arc minutes. For comparison: the Siberian radio heliograph in Buryatia has a sensitivity of 0.01 SFU and a resolution of 1.2 angular minutes.

As part of a research project to detect gravitational waves by means of long-term observation of a group of millisecond pulsars , Prof. Wang Shouguan (王 绶 琯, * 1923) suggested in 2000 that a simple L-band be used at the Miyun (密云 观测 站) observation station - Build a radio telescope with a diameter of 50 m. After working out the details (aluminum plates for the inner 30 m, welded metal grille for the edge) and the completion of the union of 5 observatories, 3 stations and the astronomical measuring device center in Nanjing to form the national astronomical observatories of the Chinese Academy of Sciences on April 21, 2001, in the second half of 2001, the Beijing astronomers obtained offers from four local institutes to build such a parabolic antenna. The designs were compared, and after considering the experience each institute had in building radio telescopes, the decision was made to go to the 54th Research Institute of the China Electronics Technology Group Corporation (中国 电子 科技 集团公司 第五 十四 研究所, Pinyin Zhōngguó Diànzǐ Kējì Jítuán Gōngsī Dì Wǔshísì Yánjiūsuǒ ), which at that time was subordinate to the Department of Electronic Warfare of the General Staff (since January 1, 2016 the Strategic Combat Support Force of the People's Liberation Army ).

The Chinese deep space network in 2013

In connection with the lunar program of the People's Republic of China , the telescope, which was completed at the end of 2005, was not only equipped with L-band receivers for 2.3 GHz, 1.4 and 1.665 GHz, but also with a cooled X-band receiver for 8.3 GHz and two S-band receivers working at room temperature for 2.15 and 5 GHz. Along with the 40-meter radio telescope in Kunming , Miyun was classified as part of the ground segment of the Chang'e missions for receiving the data from the scientific payloads. In addition to its role as a receiving antenna for payload data, the 50 m antenna is also part of the Chinese VLBI network . As part of the CVN, it can be interconnected with other large telescopes near Shanghai , Ürümqi and Kunming to form an antenna the size of China and thus also observe radio sources in distant galaxies. During the critical phases of the Chinese deep-space missions, when the probe is approaching its target, and for the precise determination of orbital data, Miyun, along with the other large telescopes of the Academy of Sciences, is used by the People's Liberation Army to assist with their Deep, which is coordinated by the Xi'an satellite control center -Space network used, originally technically separated, since 2013 networked with the military deep-space stations in Kashgar and Giyamusi via the eVLBI software developed by the Shanghai Astronomical Observatory .

After the State Commission for Development and Reform approved the space weather observation project Meridian of the National Center for Space Science and other institutions in 2006, Miyun, where interplanetary scintillations triggered by solar winds were observed with the MSRT system in 2001 , became one of the 15 participating Observatories. This enabled the Beijing astronomers to access funds to set up an IPS observation facility in Miyun. Since the 50 m parabolic antenna with X and S band receivers was already available, all that was needed was to develop decimeter wave receivers for 232, 327 and 611 MHz, and then there was a lot of data processing. After a lengthy phase of tests, troubleshooting and optimization, the IPS observation system passed its first use on September 27, 2011 in a real test with the quasars 3C 273 and 3C 279 as radio sources. Such observations are only possible as long as Miyun has no line of sight to the moon, i.e. for about 12 hours a day. Work for the ground segment of deep space missions has priority.

In addition to the 50 m antenna, the Miyun observatory also has a parabolic antenna, originally designed in 2015 as a 35 m antenna, but then with a 40 m diameter, which will be used in the Change 5 mission planned for November 2017 together with the 50 m m antenna and the antenna in Kunming should receive payload data. After a false start of the Langer Marsch 5 launcher intended for this mission in July 2017, the return mission to the moon was postponed until early 2020. In the Chang'e-4 mission 2018/19 the 40-m antenna was not used, but it should definitely at the bottom segment of the planned 2020 Mars mission are used.

In addition, a 1:10 model of the 500 m radio telescope FAST , which was then in the planning phase , was built on the east side of the site in 2004–2006, jointly financed by the National Foundation for Natural Sciences , the Academy of Sciences and the National Observatories a pit modeled from reinforced concrete, which is supposed to represent the natural karst basin at the original location in Guizhou , a ring carried by masts, the rope net attached to it, reflector elements mounted on it and above all the pulling ropes with which the focus cabin is positioned and the mirror is brought into parabolic shape. With this functional model, real observations were carried out on pulsars and HI areas in order to test and improve the technologies used at FAST. 40 ° 33 '27.9 "  N , 116 ° 58' 36.1"  E

Huairou Solar Observatory

On September 20, 1978, the Academy of Sciences approved a plan by the Beijing astronomers to build a solar observatory on an island in the large reservoir of what was then Huairou County . This was preceded by a long search for a location and it took another six years before the observatory (怀柔 太阳 观测 基地, Pinyin Huáiróu Tàiyáng Guāncè Jīdì ) could be put into operation in November 1984.

In China at that time people were particularly interested in the magnetic field and the speed field of the sun. Parallel to the construction work in Huairou, Prof. Ai Guoxiang (艾国祥, * 1938) constructed a 35 cm telescope for observing the solar magnetic field together with the technicians from the Center for Astronomical Measuring Instruments of the Academy of Sciences in Nanjing . The telescope consists of a vacuum refractor , a birefringence color filter to select the wavelengths to be observed and a polarizer to measure the magnetic field in the photosphere of the sun . This means that the vertical component of the magnetic field can be measured with an accuracy of 10 Gauss and the horizontal component with an accuracy of 150 Gauss via the Zeeman effect (the splitting of spectral lines by a magnetic field) . The sun's radial velocity field can be determined with an accuracy of 30 m / s via the Doppler shift of the observed spectral line - usually FeI 5324 Å (photosphere), sometimes Hβ 4861 Å ( chromosphere ).

The heliospheric current layer

Since 1987, Ai Guoxiang and his colleagues have been working with the Big Bear Solar Observatory in California on a worldwide project for the permanent observation of the solar magnetic field. There are also joint projects with observatories in Japan, France and Russia. In addition to the changes in the solar magnetic field, research focuses on the observation of the heliospheric current layer at the border between the northern and southern solar hemisphere, the observation of coronal holes and the three-dimensional extrapolation of the solar magnetic field on the basis of these observations.

In August 1991 a 10 cm refractor with a focal length of 120 cm was installed in the solar observatory, with which the entire surface of the sun can be photographed at once. After several years of trial operation and repeated improvements to the components, this telescope was officially put into operation in 1994. While the 35 cm telescope is a domestic product, a MegaPlus CCD camera from Kodak -Videk with 1342 × 1037 pixels and a high-resolution image processing system from the USA were used here. This means that the vertical component of the solar magnetic field can be measured with an accuracy of 1 Gauss, the horizontal component with an accuracy of 50 Gauss. Data processing does not take place in Huairou, but in the main office on Datun Street. In addition, the Huairou solar observatory still has a 14 cm H-alpha telescope for observing the chromosphere, an 8 cm telescope for observing the entire solar surface in the CaII 3933 Å spectral line, and a 60 cm three-channel telescope.

Like the Xinglong (兴隆 观测 站) observation station, which opened in 1968, 100 km northeast of Beijing, already in the area of Chengde , where optical star observations are made, the Huairou Solar Observatory is a campus of the University of the Chinese Academy of Sciences . Six professors supervise doctoral students who are working on dissertations on the subject of solar magnetic fields and the construction, automatic control and image processing of optical solar telescopes. 40 ° 18 '57.4 "  N , 116 ° 35' 40.1"  E

Shahe observation base

The Shahe observation base (沙河 观测 基地, Pinyin Shāhé Guāncè Jīdì ) was officially put into operation on June 1, 1960, initially as a timer for the Chinese radio (中央 人民 广播 电台), the then Beijing television ( CCTV since 1978 ) and the official Beijing time . At the beginning, a tube quartz clock was used , then a transistor quartz clock in the 1970s, a rubidium atomic clock in the 1980s , and a small cesium atomic clock in the 1990s .

In 1980, a twin-tube solar telescope made by the Center for Astronomical Measuring Instruments of the Academy of Sciences in Nanjing was installed, with an 18 cm refractor for observing the photosphere and a 25 cm refractor for observing the chromosphere. A 20 cm binocular telescope with an integrated theodolite for tracking satellites also came from the Center for Astronomical Measuring Instruments .

In 1986, the Shahe observation station for the perihelion passage of Halley's Comet was opened to the public. That year nearly 10,000 students, politicians, Beijing citizens and foreign tourists came to watch the comet with expert guidance. Many visitors also came to the meteor streams , for example almost 3000 in 1998. When the observatory as such was closed in 2002, the original instruments, atomic clocks etc. were left on site. According to a concept developed jointly by the National Astronomical Observatories of the Chinese Academy of Sciences and the Yurong School (北京市 育 荣 实验 学校, a kind of Waldorf school ) in the Huilongguan street district of Changping , the "Training Base of the National Observatories for the Popularization of Astronomy" (国家 天文台 天文 科普 教育 基地), where visitors can view models of ancient and modern observatories in China in an exhibition hall and, under supervision, can even observe the sun and the sky with the original telescopes. 40 ° 6 ′ 5.8 "  N , 116 ° 19 ′ 45"  E

Tianjin Navigation and Communication Center

On August 15, 2012, the National Astronomical Observatories of the Chinese Academy of Sciences began planning and purchasing land for a so-called "navigation and communication center" in Kuoliang Street, Daliang Municipality, Wuqing District in the west of the government- direct city ​​of Tianjin (天津 导航通信 中心 站, Pinyin Tiānjīn Dǎoháng Tōngxìn Zhōngxīnzhàn ). With an investment of 880 million yuan (in terms of purchasing power almost 1 billion euros), a system was to be set up that initially had 6 of its own satellites and 5 parabolic antennas set up on the site for slowly moving customers (ships or similar) in the Asia Pacific provided a positioning signal every minute, at a cost of 0.30 yuan per signal. The system should also be able to make phone calls at a rate of $ 1 / minute. With the initial set-up, the system could serve 100,000 customers, which, even if only 10% of customers used the services on a given day, would generate significant revenue for the National Observatories - it was estimated at 157 million yuan a year alone at the time the navigation service.

The groundbreaking ceremony took place on June 18, 2013 on the 4.2 hectare site. The government of Daliang Municipality generously supported the project and enabled the NAOC to begin construction and obtain the necessary permits retrospectively. As a result, 90% of the construction work had already been completed in November 2013. Since a total of 13 scientific instruments will be used on the orbiter and rover for the mission to Mars planned for 2020 , which will transmit an enormous amount of data to the ground segment of the mission in the NAOC headquarters in Beijing, the National Observatories decided to add to the existing antennas in Miyun and Kunming on the site in Daliang to set up another ground station specially for the reception of payload data, because of the signal attenuation over the 400 million kilometers distance with a large parabolic antenna with a diameter of 70 m.

On the landings of the lunar probes Chang'e-3 and Chang'e-4 there are payloads that will send data to Earth for many years to come, parallel to the Mars mission, which the antennas of the ground segment will also have to receive. The unpacking and further processing of the data encrypted with a convolutional code for the purpose of forward error correction then takes place in separate offices for the moon and Mars. Originally, it was assumed that the moon rover Jadehase 2 would have reached the end of its life in spring 2020. However, the rover proved to be unexpectedly robust and showed no signs of fatigue until mid-May 2020. Since the construction work in Daliang (and at the Kashgar deep space station of the People's Liberation Army ) was not yet completed at that time, the resources of the Chinese deep space network had to be partially withdrawn from the lunar program in order to prepare for the Tianwen-1 mission. The moon rover could then only carry out stationary measurements until further notice.

As with the 50-meter antenna in Miyun, there was a tendering process, and in June 2017, a conference held in Xi'an selected the design for the 39th Research Institute of China Electronics Technology Group Corporation (中国 电子 科技 集团公司 第三 十九 研究所, Pinyin Zhōngguó Diànzǐ Kējì Jítuán Gōngsī Dì Wǔshísì Yánjiūsuǒ ), who had already built the 40 m radio telescope in Kunming in 2005/2006. The engineering office Tiankan (天津市 天 勘 建筑 设计院, Pinyin Tiānjīn Tiānkān Jiànzhù Shèjìyuàn ) , which is subordinate to the Tianjin City Planning Department, was responsible for the planning and construction supervision of the earthworks and the creation of the foundations, and the Chinese Space Construction GmbH (工程 航天公司), a subsidiary of the China Aerospace Science and Industry Corporation . The foundation stone for the new antenna was laid at the end of October 2018, and on April 25, 2020 the dish was lifted onto the bogie. Trial operations are scheduled to begin in October 2020, so that the antenna will be ready for use when the Tianwen-1 probe is swiveled into Mars orbit in February 2021.

The antenna, which works according to the Cassegrain principle , can - like the outwardly similar radio telescope Effelsberg - rotate on a circular rail while the dish is pivoted around a transverse axis. The total weight of the 72 m high telescope is 2700 t. The 450 t bowl is laid out in 16 circles with a total of 1328 plates. The antenna has cooled receivers for the frequency bands S, X and K u . In the X-band, the efficiency of the antenna is up to 60% from an elevation angle of 10 °. It is planned to use this antenna for the mission to the near-Earth asteroid (469219) Kamo'oalewa and the main belt comet (7968) Elst-Pizarro , which is scheduled for 2022 . According to Li Chunlai , the head of the department for lunar and deep space exploration (月球 与 深 空 探测 研究 部) at the National Astronomical Observatories , however - subject to the approval of the funds by the State Council of the People's Republic of China - further recipients and specifically for them Mission-tailored data processing systems are installed. 39 ° 32 '11.7 "  N , 117 ° 5' 52.2"  E

Web links

Individual evidence

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Coordinates: 40 ° 0 ′ 16.1 ″  N , 116 ° 23 ′ 8 ″  E