of the XXVI RadioAstron Meeting

by Glen Langston

The XXVI RadioAstron (RA) meeting was called by Dr. Nicholy Kardashev to show the progress in satellite development. The meeting was held in Moscow on 2001 July 17-20 at four locations, 1) the Lavochkin Association, 2) Pushchino Radio Observatory, 3) Russian Aviation and Space Agency (RASA), and 4) the Astro Space Center (ASC). The highlight of the trip was a visit to RASA headquarters to meet with deputy directory Polishchuk. Never before had the RISC met with such a high level member of the RASA.

There has been significant progress on both the Radio Telescope and the service module since 1999, but satellite launch is scheduled for early 2005. The Russians expressed regret for the satellite delays, but the improving Russian economy has led to political support for space research. For the first time, the RadioAstron project is listed as a priority budget item in the RASA budget.

The Russians are sticking with their high orbit plans, but also point out that shorter projected baselines are easily used over a wider region of the sky than is possible with the lower orbit. Their plan seems reasonable and could lead to good results for observations of the sources known be smaller than a few micro-arcseconds. The capability Russian satellite to rapidly shift to different sources allows phase referencing, an important capability. This capability could also allow more efficient use of the high orbit by allowing several sources to be observed while near apogee.

To summarize, there has been some visible progress on the RadioAstron satellite construction and implementation of a credible test plan. A top official of the Russian Space Agency has indicated they intend to complete the RadioAstron project. Our Russian colleagues have been working hard, despite difficult circumstances and foreign support is particularly important as the testing milestones are approaching.

Summary of meeting presentations

On 01 July 17, Yuri Korneev, Astro Space Center engineer, met me at the Airport. Russia had change dramatically since my last visit to Moscow in 1994. Many buildings were freshly painted, and older buildings had been repaired. The churches had been beautifully restored. There were many more stores visible and seemed to be full of items and Russian Shoppers. There was a new highway from the Airport, so the trip to the Russian Academy of Science Hotel was fairly quick. The weather was sunny all week, but was unseasonably hot, 33C.

On 01 July 18, a bus met the foreign delegation and took us on a tour of the Lavochkin Association where the RA antenna and support module are being built. There we viewed deployment of satellite panels which took 40 minutes. The antenna structure was a new version, with both carbon fiber panels and backup structure. The deployment was successful; it started and ended with a bang, as explosive bolts are used to detach the panels before extension and also to lock the antenna in position after deployment.

After deployment, we saw the vibration test/engineering models of the Spectrum X-Gamma satellite. The RadioAstron satellite shares the same service module, providing power, attitude control and command telemetry.

After the tour, we had an excellent 3 course lunch, including caviar and salad, beet soup and chicken fried with breaded crust.

Next the Lavochkin Association presented the status of the antenna development and outlined the test plans. Dr. S.D. Kulikov, Lavochkin director, gave an introduction (in Russian translated by an assistant) and was meeting chairman. He gave a summary of satellite responsibilities. A few hundred sub-contractors provide components to Lavochkin. Spectrum X-Gamma remains the top priority and the payload modules have been completed. RA is the second in the series and an Ultraviolet telescope is the third satellite in this series. The UV satellite will have 1.7m diameter mirror.

Lavochkin is working in all three main space programs, planetary, astrophysics and solar studies. They intend to have all three missions launched by 2006. Their most recent communications satellite was launched a few months ago.

A.S.Astavin presented "Status of development and tests of SRT Antenna". They are working to achieve surface accuracy of 0.8 mm maximum deviation, with maximum deviation of 2 mm between panels. They expect 20 year lifetime of telescope structure. The 27 panels are composed of carbon fiber with titanium components structure. Thermal deformations of the structure are dominating the distortion budget. After adjustment for overall panel position, the rms accuracy was 0.7 mm without any additional adjustment. Surface variation over a reasonable temperature range is 0.4 mm.

The RA model will also be used as the basis of the Millimetron antenna. There is a detailed document describing the RA constrains on pointing, relative to the sun. Current estimates suggest that 64% of sky may be observed at any one time.

V.E. Bitkin presented "Fabrication of SRT antenna panels." He works for a large company (largest plastic plant in Europe). Requirements for structural stability are 10^{-5} and required use of carbon fiber. Mathematical models were required to develop a multi-layered scheme for the panel development. Multi-layered panels required development of a new manufacturing scheme. (Note that the room temperature was very high, and the talks were given twice, once in Russian with an English translation after each phrase. So keeping awake and taking notes was difficult). Central mirror meets the requirements. There were some questions about the effects of thermal cycling (by +/- 50 C) and development of micro-crystals, but tests after thermal cycling suggested that the carbon fiber material was not adversely effected.

M.E. Bolotov presented "A study of adjustment of SRT antenna petals". He looked at long term temperature variation effect on antenna shape. He assumed perigee = 3000 km and apogee = 80000 to 350000 km. Complicated problem due to shading of the structure by the back-up structure. Remarkably wide variation in temp on panel, from +47 to -90 C. So this corresponds to 150 C in a substance that has10^-5 so in 3m have 3*150 * 10^-5 = 5x0-3 = 5mm. However only distortions perpendicular to the panel surface are important.

A.N. Kotik presented "A Study of Surface deformations". He felt that most concerns have been considered, but I had trouble understanding what he was talking about. Question I had was whether a thermal shield was sufficient to avoid most of these problems.

A.A. Orlov, presented "Development and tests of LNAs". The receiver package was completed 5 years ago and remains unchanged. They decided to use passive cooling and considered one and two stage systems. They can get to about 100 K with this technique. Using a heat pipe with two stages (containing different transfer media) in the stages, they can meet the 100 K requirement. The first stage reaches about 130 K and the second structure reaches 100 K. This system has been build and the next step is to integrate it into the satellite.

V.E. Babyshkin presented "Spectrum satellite series tests". They have finished tests of link antenna and design model. Expect to complete full tests by November 2002 for Spectrum X-Gamma. They were delayed in obtaining control computer (until august) to run tests and integrate into engineering model. They have a large solar panel capacity, expecting 2.6 K-watts total, including 0.9 K watts for science. They have 28 Amp hours in hydrogen batteries.

On 01 July 19, we got a late start (due to bus problems) on our tour of Pushchino Obs., which is 100 Km south of Moscow. We arrived to the 5 sq km site which has several telescopes. The largest parabolic antenna was a 22m diameter telescope operating at 1.3 and 0.8 cm. Primary research telescopes are large arrays with 300m by 30m cross antenna at low frequency (40 to 150 MHz) and a 200m by 400m 112 MHz phased array.

We toured the newly completed satellite test facility (called the pentagon) where the satellite will be installed for Radio Astronomy integration tests. In these tests, the Pushchino tracking antenna will act as a VLBI antenna to allow complete end-to-end testing of the system.

After the tour, we had another excellent lunch (with Armenian wine). The Pushchino Observatory had very good conference room facilities and we reconvened there, where Dr. Kardashev presented RA time line. He summarized the significant improvement of carbon fiber structure. They anticipate having the satellite astronomy package Engineering/Flight model completely assembled at the end of 2002 for tests using Pushchino site.

The are making the changes to the link subsystem required for the 340,000 km apogee orbit. They have a new 40 W TWT downlink transmitter at 15 GHz. They have changed the link antenna to allow simultaneous S, X and Ku band telemetry. The support module certification for spectrum X-Gamma will apply to RadioAstron. After the end to end testing, they anticipate using Pushchino 22m for uplink and downlink.

V.V. Andreyanov presented "Subsystem test results and plan for SRT and Interferometer plan of tests for integration of sub components". They have partially completed many components and hope to perform compatibility tests with next year. They ran Zero Baseline Interferometer and appeared to have a functioning formatter for encoding the astronomy data. They used same formatter and NRAO decoder for Zero Baseline Test.

V.E.Babyshkin presented the "RA Time line development". The time line shows an early 2005 Launch. Satellite integration is in 2003. They plan the Pushchino test at end of 2003.

I described the GBT capabilities and summarized our tracking support for HALCA. The GBT can support all RA bands. Test plans for late 2002 were suggested, to completely test the interfaces described in the RA handbook. There were a number of questions concerning the availability of the NRAO station for tests in 2002 and 2003. V.I. Slysh summarized the "Russian Radio Telescopes". There are a surprising number of large (64m) telescopes operating at the RA bands. There is also a mini (3 antenna) VLBA with 32 m antennas (there were a total of 6 planned but 3 are now in other countries). Two of the Russian 32m antennas have observed with HALCA. RA will have very good Russian ground support.

Surgey Likhachev and Yuri Korneev presented "Multi-frequency synthesis". Results seemed good for their tests of different frequency bands during a single observation to obtain better UV coverage. They were able to produce very good results for a set of real and simulated data sets. There were questions about spectral dependence problems for deconvolution. The Yuri Korneev, an engineer, showed a scheme of generating various frequencies while leaving receiver changes minimized. Note that Finish 1.3cm system does not support a wide band, and the NRAO (Map compatible) 1.3cm LNAs are needed for this system.

Dr Konovalenko presented the "Ukrainian participation in RA". Ukraine has 6 antennas which belong to 3 different Ukrainian Organizations. Large arrays are actively used for astronomy. There is a lot of activity in LOFAR like arrays. They have a prototype active antenna array. They are well funded due to the commercial success of their satellite launch program.

On Friday 01 July 20, the RA group met with Mr. Polishchuk at Russian Aviation and Space Agency (RASA) Headquarters to learn the interest of RASA in RA. He is a deputy director general of the agency. This was the first time the RA group has ever met with such ranking official.

He made a fairly long introduction and welcome. The RASA had an internal meeting to plan a strategy for the Spectrum series. Some time ago, there was a positive response from ESA on making Spectrum X-Gamma an international project. NASA reported that if ESA supports the Spectrum series, so would NASA. Then ESA changed their plan and declined to provide $ 20,000,000 to complete the 2003 X launch and 2004 RA launch. This has lead the most recent delays. Polishchuk stated that Russia has implemented all its promises for 1999-2001. RA is a top priority for the RASA, and believe it is important for the Russian Science Community.

Dr Kulikov of Lavochkin was given the floor. He summarized our activities at Lavochkin. Kardashev was happy with the presentation and looks forward to completion of the satellite. He was worried about the age of the delivered receiver components. Appreciated the components that were delivered by outside agencies and by the tracking support.

They anticipate display of the opening the antenna at the next meeting with NASA. Holmes asked whether there was any additional items that should be directly communicated to Dr. Weiler at NASA. Polishchuk's answer was that they had been in frequent communications and the agenda was set.

Kess van't Klooster of ESA asked "since the ESA response on Spectrum X-Gamma was negative then what will happen with Spectrum RA?" Polishchuk's response was that nothing yet has changed. and they are looking for options to solve the problem.

The planned suspension of NASA tracking support in Feb 2002 will adversely effect satellite testing. Others noted that the lack of the definite launch date is preventing significant foreign contributions. Polishchuk responded that the RASA declared 2005 launch back in 1999 at IACG. He noted that next year RA has specific line in the RASA budget in the priority mission section.

We took a quick lunch break and then were driven to the Astro Space Center (ASC) for a mission science meeting at 15:30. Meeting was started by Kardashev, giving list of top science targets. He claimed that frequency synthesis allows a number of sources to be observed at any one time, on shorter projected baselines. With proper use of multi-frequency synthesis, structural changes can be monitored, even with only 1 D uv-coverage.

Norbert Bartell spoke on "Phase Referencing". Noted that in the near future optical observations will reach 1 micro-arcsecond resolution. The capability of RA to rapidly move between nearby sources is very valuable for phase referencing. The assumed RA position uncertainty limits astrometry. Norbert described a number of astrometry experiments, including AGN, pulsars, masers and satellites.

Ed Fomalont showed some "VSOP survey results and its motivations". The VSOP Survey has 289 sources but was only able to observer about 200. Have a plot of average correlated flux density versus baseline length. The survey results show that 30 % of sources are smaller than 0.25 mas. 40% has structure between > 0.9 mas and < 2mas and 30% in structure > 2mas.

During the coffee break we were given a quick tour of the test electronics test facilities. The NRAO Data Decoder was installed as a part of the test system. They have list of requested changes to the decoder. The RA receiver has a concentric feed system with all 4 in a single line. This package was completed a few years ago.

Jim Lovell presented a study of "Inter Day Variable sources (IDVs)". An IDV is variation by 3 sigma in 36 hours. His sample is monitored by the AT. Three show strong variable by > 10%, and some show quasi-periodic variations. Sample includes 6 BL Lacs and 16 of quasars. They favor interstellar scintillation as the explanation for the variability, but this still requires very small source structures < 10 micro-arc-second. Some sources show fairly short big, episodic variations. Some show 2 or 3 hours time scale of variations.

A.P. Lobanov presented "Effelsberg contributions to VSOP". The MPI in Bonn has contributed 40 Days of observations. He presented VSOP work that has resulted in several publications. One by Bower showed high brightness temperature sources. Porcas showed phase referencing results. Tests of phase references show that orbit accuracy was very good and phase referencing is possible. Lobbanov showed his work on a very nice image with resolution of the jet of 3C273, divided into two components spiraling along a common axis. Presentations will be sent to Misha Popov for publications. 1) Action to determine what steps to achieve 1 m orbit accuracy, in order to allow phase referencing. 2) Action to ask NASA/NRAO for support of tracking stations for 2002 and 2003, while the satellite test plan is being implemented. 3) Want NRAO to write contract for LNA at 1.3cm. Ed Fomalont and Glen Langston will ask NRAO CDL to speed up their response. 4) Test interfaces of GB station and Astro Space Center Mission operations.

Leonid Gurvits reminded us that Lavochkin has made good progress despite the very harsh conditions. He also noted the continual slip in projected launch date. He was concerned that although the recent progress is good, but that due to the long history of delays, the Russian Space Agency must provide the highest level of assurances to ESA and NASA in order to get their continued support.

We also discussed the next RA meeting. Probable next meeting could be August 25, 2002 in Moscow, just after the URSI meeting in the Netherlands.


The RA group is still working hard for the mission, and the highest levels of the RASA have expressed intent to complete RA. If there was not a such a long history of RA delays, we would expect a satellite launch in 2005.

Mr. Polishchuk of RASA, implied that external funding at the $20,000,000 level could assure the speedy launch of the Spectrum Series. The RASA is looking for alternative funding sources and indicated that they remain intent on completing RA in 2004 and launching in 2005.

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