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Status Report on the 13.7 m MM-Wave Telescope for the 2015-2016 Observing Season


Ye Xu, Yingxi Zuo, Xuguo Zhang, Zhenqiang Li, Yang Li, Xinghai Pang, Jibin Li, 

Wenhao Liu, Binggang Ju, Jixian Sun, Dengrong Lu,Min Wang, 

Kun Yan, Yongxing Zhang, Ping Yan 

Qinghai Radio Observing Station of Purple Mountain Observatory, CAS 

Delingha MM-Wave Observing Station  


  1. Overview 

   During this summer (Jul.-Aug. 2015) — the maintaining and upgrading season— telescope mechanical transmission

 and superconducting receiver system have been inspected and maintained. Up to August 16th all the maintaining and

 upgrading items in schedule have been completed successively. 

  The comprehensive performance astronomical tests were started on August 16th and lasted two weeks. The tests

 include pointing, sub-reflector focusing, power pattern of the nine-beam receiver, interval and efficiency array of

 the 9 beams, intensities and velocities of standard sources, etc. 

The main contents and results of the maintenance, upgrading and test are briefly reported as the following: 

1. The high-speed box system was upgraded. [2] Coils and bearings of DC motors that used in the 13.7m  telescope

    were so worn that often broke down. In addition, there are no substitutes in the market. For the  sake of proper

    operation of the telescope, Nanjing Astronomical Instruments Research Centre was  consigned to redesign and

    rework the high-speed box in the light of existing motors of the market.   The high-speed box was upgraded this

   summer and operated properly in accordance with the design requirements after a period of trial operation. 

2.Mechanical system of main reflector and sub-reflector were inspected. [19] Still by the contract,detailed inspection

  of the mechanical system was managed by Nanjing Astronomical Instruments Research Centre, all the axle-bearings

  and gear-wheels were cleaned and oiled.  

3.Main reflector panel of antenna was cleaned. [19] After operation of an observation season, the  parabolic surface

   was covered by dust, which seriously affected the performance of the telescope. During the summer maintenance, 

   the telescope panel was thoroughly cleaned and maintained so as to ensure the reflection and efficiency of the

   telescope, and prolong service life of the main panel.

4.Chopper wheel modulator was improved. [4] This work accomplished beam modulation function and  thus

   achieved the modulation observation of continuum, which enhance the ability of observing weak signal sources of

   the telescope. The modulator modulation reference frequency could be switched arbitrarily in the range of 1Hz to

   30Hz and operated reliably. When modulation reference frequency   was 30Hz, its transition time was 15 seconds. 

5.Receiver system was maintained. [3] All systems of the receiver were inspected, upgraded or replaced,  including:

   (1) replacing cold head; (2) replacing part of cables in Dewar; (3) Replacing part of HEMT amplifiers; (4) Cleaning

  dust in compressor, FECU system, FFTS system and frequency synthesizer;  (5) maintenance of HBT amplifiers;

  (6) Replacing fan bearing of the compressor; (7) designing and processing the new blowing machine of Dewar


  1. Performance 

  1. Surface 

  The Delingha mm-wave telescope is an alt-azimuth mounting telescope. The diameter of the primary reflector disk is

13.7 m (45 feet). The optical system is Cassegrain, with the receiver working at the Cassegrain focus. After the

maintaining and upgrading season, the surface accuracy of the main reflector is 73μm, [1] the profile accuracy of the

 main reflector is 73μm. [1] According to the experience of the main reflector adjustment once a year, the profile

 accuracy showed no obvious change after one-year operation, so the profile accuracy adjustment was decided

to completed every two years. The main reflector was not adjusted in 2015. 

  1. Tracking 

  Our tests [5] indicate that the tracking error is rms=1.29” in AZ, and rms=1.33” in EL. For the most part of

 sky, the tracking error is around 1-3”, which can fulfill the needs of astronomical observations (based on the beam

 size of telescope,tracking error less  than 5” will guarantee the accuracy). Figure 2.2.1 shows the tracking errors in

 AZ and EL. 


Figure 2.2.1 Histograms of the tracking errors in AZ (left) and EL (right).  

98.5% below 3” in AZ98.6% below 3” in EL. [5] 

  1. Pointing 

The “five-point pointing observation” toward planets (Jupiter etc.) in “continuum total power receiving mode” was

 performed,and so was the “five-point pointing observation” toward line emission point sources, such as planetary

nebular and SiO2-1maser sources. In 3 days observation, 1361 groups of data were fitted by modified 

pointing model. From 2006-2007 observation season, a pointing model with 10 parameters was applied to fit

southern and northern separately. This kind of model works well in the whole sky. Figure 2.3.1 shows the sky

coverage of a pointing event. Figure 2.3.2 is the residue distribution of the fit in the southern and northern sky.

The results indicate that the pointing error is rms=3.4” in south [7] and rms=4.9” in north [7]. During the

 comprehensive test, “pointing observation -> model fit -> modification and check” process was carried

out many times (repetition was necessary). Repeated tests indicate that the whole sky pointing error is less than 5”. 


Figure 2.3.1 Sky coverage of Venus, Jupiter, Oria and X-cyg in the south[6] 

and NGC7027, R-Cas, TX-Cam in the north[7] 

during the “five-point” punting calibration observations . 


Figure 2.3.2 The residue distribution in AZ and EL after the fitting. left: for the southern sky, with the major axis of

2.7” and minor axis of 2.1”, the position angle is 25.2°[6]. right: for the northern sky, with the major axis of 3.9

 and the minor axis of 3.1”, the position angle is 40.2°[7].  

  In the subsequent observation period, the pointing condition will also be checked periodically by observing the

CO lines toward some point sources (e.g. some late-phase star like IRC+10216) or some extended CO sources

with definite distribution features (e.g. S140 etc.). As a routine test item, the pointing status is tested and verified

 every month in an observation semester. 

  4.Intensity scale and efficiency  

  Using standard chopper-wheel calibration method (Ulich & Haas 1976, ApJS, 30, 247, and references thereafter) for molecular lines, the temperature thus derived is the one corrected for the atmospheric and ohmic attenuation, which is denoted as TA* in the literature. For extended sources, this temperature needs further correction by the main beam efficiency ηmb to yield a "observational radiation temperature" TR*, which can be compared with results obtained from other telescopes of the similar type. This temperature is the convolution between the ideal main beam and the source brightness temperature distribution. Notice that all the 12CO, 13CO and C18O original data has been calibrated by the beam efficiency according to. 

  The half-power-beam-width (HPBW) reflects the resolution ability of a telescope, which can be calculated by HPBW=kλ/D, where λ is the working wavelength, and D is the aperture size, and k depends on the illuminating function. At a local oscillating frequency of 112.6 GHz, for USB (115.2 GHz) the HPBW is 48.4±1.9’’ in AZ and 49.8±2.0’’ in EL, for LSB (110.2 GHz) the HPBW is 50.8±1.9’’ in AZ and 52.3±2.1’’ in EL [8]. 

  The two-dimensional distribution of the beam can be obtained by scanning over an object. Figure 2.4.1 and 2.4.2 are the OTF two-dimensional scanning results of Venus [8]. Figure 2.4.3 and 2.4.4 are the OTF one-dimensional scanning results of Venus [8]. 




Figure 2.4.1 The telescope two-dimensional power pattern obtained from OTF observing to Venus. (USB: 115.2GHz) The regrid step is 20”. 


Figure 2.4.2 The telescope two-dimensional power pattern obtained from OTF observing to Venus. (LSB: 110.2GHz) The regrid step is 20”. 


Figure 2.4.3 EL dependent intensity distribution from one-dimensional scanning of the Venus in AZ (beam5, USB: 115.2GHz). During the observation the step is 10″,

the integration time of each position is 5 sec, and the absolute intensity calibration has been used to get the data of antenna temperature. 


Figure 2.4.4 EL dependent intensity distribution from one dimensional scanning of the Venus in AZ (beam5, LSB: 110.2GHz). During the observation the step is 10″, the integration time of each position is 5 sec, and the absolute intensity calibration has been used to get the data of antenna temperature. 

  The moon efficiency is the reflection of beam efficiency when observing an extended source. After the pointing work we set the local oscillating frequency to 112.6 GHz and scanned the moon in one dimension. After the moon phase correction, we obtained the moon efficiencies [10] of nine beams for USB and LSB listed in table 2.4.1.  

Table 2.4.1 moon efficiency of USB and LSB of nine beams 

Side Band 






























  The moon efficiency is higher than the beam efficiency obtained from observations of planets. The reason is that the former includes contribution from forward side lobes. In the practical observations of some molecular clouds whose scale usually is greater than the beam widths of telescope, the beam efficiency is closer to the moon efficiency. However, usually this is not wanted by observers, as the side lobes receive radiation from directions other than the targeted position. Therefore, in the observation toward an extended source, lower forward side lobes are needed. When the side lobes can be effectively suppressed, the main beam efficiency obtained from observations of planets will get closer to the moon efficiency. 


Figure 2.4.5 Intensity distribution from one-dimensional scanning of the moon. During the observation the receiver LO is 112.6 GHz, the scanning rage is ±1500″the step is 20″. [10] 

The moon phase ranges from -280.68° to -280.90°, the moon brightness temperature is 170.3K~186.2 K.Left: USB (115.2GHz). Right: LSB (110.2GHz). 

  For a telescope that is mainly used to observe extended sources like molecular clouds, its main beam efficiency is a very important parameter. Ideally, With the purpose of measurement of main beam efficiency, an astronomical object with the same size as the telescope beam size is needed. However, in fact, there is no such an astronomical object (or artificial object) can meet the requirement. Therefore, the main beam efficiency is obtained by observing the moon, the planet, extended source with line emission, point source with line emission, etc. In the five-point pointing observation, we get the temperature results by calibrating the observational results with the foreground black-body source, and get the telescope beam width at the mean time. These results enable us to estimate the aperture efficiency and the main beam efficiency of the telescope.  

  Currently a 3×3 beam superconducting receiver is used in the 13.7m MM-wavelength telescope. Precisely measurements of the interval matrix and the efficiency matrix of the nine beams are necessary. In the testing, using five-point observations of the nine beams rotation toward continuum sources and CO sources of high signal-to-noise ratio, we fitted and then obtained the beam width, peak intensities, position errors etc. of each beam. Then, the main beam efficiency and aperture efficiency of the central beam (the fifth beam), as well as the interval matrix in AZ and EL direction relative to the central beam could be estimated. Results are presented in the following figures.  


Figure 2.4.6 The relation between main beam efficiency and the EL of the pointing center (5th beam). Left: USB (115.2GHz); Right: LSB (110.2 GHz). [8] 


Figure2.4.7 The relation between aperture efficiency and the EL of the pointing center (5th beam). Left: USB (115.2GHz); Right: LSB (110.2 GHz). [8] 

Using the von Hoerner-Wong efficiency of structure function (equation 1) to fit the efficiency test results, we obtained a series of parameters, which are not only accordance with the actual case of telescope but also comprehensible in physics. [12]  


Fitting results are listed in table 2.4.2 [8]. 

Table 2.4.2 Fitting parameters of main beam efficiencies for USB and LSB 






















  Using five points tracking observation mode with beam 5 toward Jupiter, the local oscillating frequency was set to 86GHz, 88 GHz, 96 GHz , 98 GHz , 104 GHz, 110 GHz in turn. Results are listed in table 2.4.3. [8] 

Table 2.4.3 Main beam efficiencies, aperture efficiencies and beam widths in different frequencies. 
















Main beam 
































HPBW_AZ (") 















HPBW_EL (") 
















Figure 2.4.8 Left: the relation between aperture efficiency and frequency; Right: the relation between the main beam efficiency and frequency [8] 


Figure 2.4.9 The relation between beam width and the observing wavelength [8] 

The relation between the beam width and the observed wave-length can be formulated as follows: [8] 



The testing results of interval matrix are listed in Table 2.4.4. [11] 

Table 2.4.4 Beam interval matrix 































  During the efficiency matrix test, the standard sources of S140, DR21, NGC2264 were observed by the nine beams in sequence. The normalized efficiency matrix relative to the central beam was obtained by calculating the ratio of peak intensities as well as integrated intensities of 12CO and 13CO between each beam and the central beam. Results are listed in Table 2.4.5. [13] 

Table 2.4.5 beam efficiency matrix 

Side Band 










USB (115.2GHz) 










LSB (110.2GHz) 










   Regarding the telescope as a whole system, the observational accuracy of standard line sources usually reflects the practical accuracy which can be achieved. In the operation, we consider it as an indicator of the instrumental performance and status, validity of observation procedure and data processing. 

Due to the gravitational deformation of the antenna disk as well as the optical coupling changes, the antenna temperature observed depends on the elevation angle to some extent. During "astronomical tests of comprehensive performance", extended line sources S140 and NGC2264 were observed in their central points. And the whole observable elevation angles were covered. The observation results are corrected by the efficiency correction formula measured above and the efficiency matrix, then the relations between spectrum peak intensities and elevations are obtained and shown in Figure 2.4.10 and 2.4.11. 


Figure 2.4.10 The 12CO peak intensities of S140 from nine beams according to different EL.  

Data have been calibrated by efficiency matrix and main beam matrix [14] 


Figure 2.4.11 The 13CO peak intensities of NGC2264 from nine beams according to different EL. Data have been calibrated by efficiency matrix and main beam matrix [14] 

  In Figure 2.4.10 and Figure 2.4.11, we could see that the variation of 12CO1-0 peak intensities for standard source S140 in the north and 13CO1-0 peak intensities for standard source NGC2264 in the south, calibrated by the efficiency matrix together with the main beam efficiency, show little dependencies on EL. And an entire scanning by OTF observation could eliminate such effect, which averages over the points with different ELs.  

  1. Receiver 

  The SSAR is a MM-wavelength 3×3 multi-beam receiver, the data production rate is about 25 MByte/s. This instrument mainly includes: 9 Sideband Separating SIS mixers, no tuning digital LO source, all digital bias power supply, independent IF model, broad band high resolution digital spectrum analyzer, and many other new techniques, which successfully accomplished integrated multi-beam receiver system for MM wave band. This is the first MM-wavelength multi-beam receiver which is based on sideband separation technology in the world. And also, it is the first multi-beam receiver in the field of radio astronomy in China. The frequency range of the SSAR receiver is 85-115 GHz. In this season, when the LO frequency is working on the range 86-112.6 GHz, the measured value of receiver noise Trx is shown in Figure 2.5.1 [16], the system temperature Tsys (including effect of the atmospheric and dome) is shown in Figure 2.5.2 [17]. Observers can estimate the integration time and sensitivity of the receiver from these data. 


Figure 2.5.1 TRX at different frequency points. The x-axis denotes beam number, the y-axis denotes noise temperature of one side band. Different shapes denote different LO frequencies[16]. 


Figure 2.5.2 Distributions of system temperatures (LO frequency @ 112.6GHz). The x-axis denotes beam number, the y-axis denotes system temperature of one side. Filled red circles denote LSB receiver (110.2GHz); black filled squares denote USB receiver (115.2GHz). The system temperature includes noises from the receiver, the antenna and the optical system, the dome, the membrane and the atmosphere. [17] 


Figure 2.5.3 The stability of the receiver (The data sampling rate was 3 Hz. One data line get from IF detector output by 1 hour were used by Allan variance analysis . [16] 

  In this observation season, telescope will work in the whole 85--115 GHz frequency band. Multiple measurements demonstrated that, when the SIS mixer works at the first step, the ten-minutes normalization stability is ΔG/G 410-3 . Figure 2.5.3 shows the typical results of normalization stability measurements in the working frequency range. 

  1. High-resolution digital spectrum analyzer 

  The SSAR system installed into the 13.7m telescope has a backend made up of 18 high resolution FFTS digital spectrum analyzers , which can work at 1000 MHz or 200 MHz. And Each band has 16384 channels. This spectrum analyzer was successfully tested on the telescope in April, 2007. The results indicate that those 18 digital spectrum analyzers break through in key technical marks such as bandwidth, resolution, dynamic range, stability, etc. It demonstrates potential for receiving extra-galactic spectrum lines, making high resolution observations, and performing deep integration. According tests, the Allan time of the whole receiver system, taking atmosphere variation into account, is greater than 100 seconds no matter which bandwidth the FFTS work at [15]. FFTS can simultaneously receive multiple spectral lines. Observers can know more with the help of “calculation software for observing line frequency (FFTS freqset)” (availible for download in our website: http://www.radioast.csdb.cn/tools.php). 

Talbe 2.6.1 Main parameters of the telescope FFTS backend 




Channel frequency interval 


Channel velocity interval 


Channel frequency interval 


Channel velocity 



1000 MHz 





7. Data storage 

  To store huge amounts of data produced by OTF observation, a data storage system is equipped, which consists of two DELL Powerage NX1950 with Scientific Linux 5.4 operating system and four EMC store cabinet. The storage capacity is 40 TB, and it is also used for OTF data preprocessing. 

  1. Observing mode 

In receiver operating frequency range, telescope works at single sideband using position-switch mode to operate single point observation. 

Using “superconducting imaging spectrometer” and OTF mode to observe lines of CO and its isotopes simultaneously. 

The standard chopper-wheel method is used for temperature calibration. 

Measurement of the atmospheric opacity at 3 mm can also be conducted. 

Pointing, mapping, or OTF observation for continuum emission. 

9. Data format 

 The data output is in the international standard FITS format. Observers can use GILDAS/CLASS or other software to reduce and process data.  

 Notice that GILDAS/CLASS is a piece of software used for processing radio astronomical data, which was jointly developed by Grenoble observatory and IRAM. 

  1. Data Downloading 

The observation data can be downloaded from the database on the website of http://www.radioast.csdb.cn and http://mirror.radioast.csdb.cn. To download the unpublicized data, observer need to log in. The user name is the observer’s issue number and the password is given by the observation assistant. Observer can look over the observational records on the website http://www.radioast.csdb.cn/viewrecord.php . 

  1. Application and Scheduling 

In 20152016 observing semester, the up-to-date information of Delingha 13.7m MM-wavelength telescope will be posted on the website of our site in time: http://www.dlh.pmo.cas.cn. 

  1. Project examples of the telescope in the several previous semesters 

1. Detection of physical structure in Galactic molecular clouds; 

2. High speed gas outflow and dynamics of young stars; 

3. Interstellar chemistry; 

4. Molecular gas distribution in the Galactic star-forming regions; 

5. Galactic dynamics; 

6. The interaction between the supernova remnant and interstellar medium, cosmic ray sources; 

7. Molecular gas observation of the stellar evolution and the late-type stars; 

8. Molecular line observation of the solar system objects; 

9. Observational study of the moon radiation in the MM band; 

10. Observational study of the propagation and transmission properties of MM radiation in the terrestrial atmosphere. 

11. Observational study of the Starburst Galaxies. 

  1. Using the telescope 

1. Data progressing and backup 

The data storage system is also used for OTF data preprocessing, the pre-processed data will be uploaded to “Millimeter Wave Radio Astronomy Database (http://www.radioast.csdb.cn)”. For data downloading, observer needs to log in the database website and then click “download CLASS format data” to go to data download web page (user name and password are offered from observation assistant). Observational data by Position-switch observing mode is single point FITS files and CLASS format files (14m file), and after regrid, the data by OTF observing mode is CLASS format files (.bur file) of 30″×30″ pixel size, the bur files from multiple observations to the same source will be combined into a fitscube file. The appointed assistant could provide help with the data processing process. 

  There is a backup of the observation data in Computer Network Information Center, Chinese Academy of Sciences, where also has a mirror website of “Millimeter Wave Radio Astronomy Database (http://mirror.radioast.csdb.cn)”. Observer could also download data there. 

After one year of exclusive occupation of the data by the project PI, the data will become open and shared, according to the international convention. Cross-year projects will become open and shared one year after the last day of the project. Anyone could download the open and shared data from “Millimeter Wave Radio Astronomy Database”. 

  1. Transportation and living service 

Supportive services are provided by the observatory, including reception, accommodation, transportation, Internet connection, and emergent oxygen service. The working and living conditions at the observatory have been improved a lot after decorations in the summer of 2003. Observers have to pay for the accommodation and transportation by themselves. As the site is in the northwest China, where the transportation is not very convenient, we suggest the visitors book the tickets ahead of time. Now, users can book train ticket with their identification information in Sinorail Customer Service Center website: http://www.12306.cn, after registration in the website, users can access to the services for train schedule inquiry, valid tickets inquiry, price inquiry, booking tickets (including online payment), order inquiry, ticket alteration, return of ticket etc. Please order the ticket by yourself, our site will no longer provide ticket booking service for visitors. 

We offer transportation services from Delingha train station to our observatory. Please contact Mr. Binggang Ju of the arrival time and detail requests in advance. The telephone number is +86-0977-8224969. 

The Delingha station is located in the Qinghai-Tibet Plateau, where the weather is dry and the oxygen is rare, and the winter is severely cold. Visitors should bring enough warm clothes and get well prepared. 

  1. Suggestions, comments and further information 

The upgrade and reformation in this report and the astronomical tests of comprehensive performances are conducted in joint effort of the staff in the observatory and the millimeter-submillimeter wavelength laboratory, as well as the CAS Nanjing Astronomical Instruments Center and the star formation group of purple mountain observatory. For further information, please contact our Professor Ye Xu (xuye@pmo.ac.cn); any comments (including any questions or criticisms about this report) or suggestions can also be sent to the address. Any suggestions or comments on the astronomical or technical problems, as well as the logistic services, are all welcome. Email addresses of all the staff members can be found in our homepage: 



  1. 李阳、孙继先、左营喜、符广龙、颜昆、周剑晟、王海仁、钱元、杜心语、刘昌儒、蒋兴为、亓晓彤,2014.7.25,《2014天线面板调整总结v1.2》,德令哈毫米波观测基地; 

  2. 李阳、孙继先、张永兴、颜昆、李积斌、张旭国,2015.9.21,《13.7米望远镜电机及高速箱更新》,德令哈毫米波观测基地; 

  3. 运行组,2015-09-19,《斩波轮调制控制器的改进及测试》,德令哈毫米波观测基地; 

  4. 运行组2015.8.18,《2015年夏季维护小结》,德令哈毫米波观测基地; 

  5. 孙继先、李阳、颜昆、张永兴,2015.8.16,《跟踪误差测试报告20150814》,德令哈毫米波观测基地; 

  6. 孙继先、逯登荣、颜昆、张永兴、颜萍,2015.8.18,《五点指向观测快报(南天)(2015- 08-18)》,德令哈毫米波观测基地; 

  7. 孙继先、逯登荣、颜昆、张永兴、颜萍,2015.8.18,《五点指向观测快报(北天)(2015- 08-18)》,德令哈毫米波观测基地; 

  8. 孙继先、逯登荣、颜萍、李振强,2015.9.1,《波束效率测试(20150831)》,德令哈毫米波观测基地; 

  9. 逯登荣、张永兴、颜萍,2015.8.25,《方向图扫描快报(2015-08-25)》,德令哈毫米波观测基地; 

  10. 逯登荣、孙继先,2015.9.10,《月面效率测试报告(2015-09-10v1.0》,德令哈毫米波观测基地; 

  11. 孙继先、逯登荣,2015.8.21,《波束间隔矩阵测试报告(2015-08-20)》,德令哈毫米波观测基地; 

  12. 杨戟,2008.8.16,《关于进一步提高13.7米望远镜天线面精度的技术路线图v1.1》,德令哈毫米波观测基地; 

  13. 王敏、孙继先,2015.8.29,《标准源观测报告(波束效率矩阵、视向速度等)(2015-08-28)》,德令哈毫米波观测基地; 

  14. 王敏、孙继先,2015.9.25,《标准源观测报告(2015-09-21)》,德令哈毫米波观测基地;  

  15. 逯登荣,2014.10.8FFTS Allen方差测试(2014-10-08)》,德令哈毫米波观测基地; 

  16. 张旭国、刘文豪、李振强、董虎林、李积斌、庞兴海,2015.8.4,《2015TRX测试结果通报》,德令哈毫米波观测基地; 

  17. 刘文豪、张旭国,2015.8.18,《2015tsys测试结果通报》,德令哈毫米波观测基地。 

  18. 逯登荣、孙继先,2015.10.1,《方向图扫描快报(2015-10-01)》,德令哈毫米波观测基地。 

  19. 运行组,2015-08,《夏季维护及望远镜天线检修简报》德令哈毫米波观测基地; 

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