Author Topic: Russian RadioAstron (Spectr-R) update  (Read 38732 times)

Offline Salo

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Russian RadioAstron (Spectr-R) update
« on: 11/19/2011 08:45 AM »
The home page for the RadioAstron Project
http://www.asc.rssi.ru/radioastron/

Plasma-F experiment
http://www.plasma-f.cosmos.ru/en/node

RadioAstron booklet, ASC 2007
http://www.asc.rssi.ru/radioastron/_files/booklet_en.pdf

Science priorities of the RadioAstron space VLBI mission. N. Kardashev, Glen Langston, AAS 2007
http://www.asc.rssi.ru/radioastron/_files/ra_aas07.pdf

The RadioAstron User Handbook:
http://www.asc.rssi.ru/radioastron/documents/rauh/en/rauh.pdf

Some information about project:
http://www.roscosmos.ru/main.php?id=363
« Last Edit: 11/24/2011 05:38 PM by Salo »

Offline Salo

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Re: Russian Radioastron (Spectr-R) update
« Reply #1 on: 11/19/2011 08:46 AM »
News of the RadioAstron mission

by Larisa Likhacheva, larlikh@asc.rssi.ru
Boris Novikov, nbs@mx.iki.rssi.ru
 
At present all systems and units of the SC "Spectr-R" work in a normal mode.
 
•  August, 23d  -- As well as it has been planned on August, 21st the session in the domain of a perigee (90000 km) between the SC (switching on of a basic transmitter (40 Watts) of the VIRK) and the ground tracking station (TS) has taken place.
Pointing of the VIRK sharp directional antenna to the TS was carried out. The session has passed successfully at regular temperature of the transmitter and normal level of a signal-to-noise ratio (52 dB). The signal was received by the TS at Pushchino.
 
•  August, 18th -- full engagement of the high informational radio channel (VIRK) transmitter has been done. In connection with some features of SC position in the orbit currently the Pushchino tracking station (TS) "has seen" a side lobe of the VIRK directional pattern.  A complete session SC -- Pushchino TS is planned on August 21st
 when the SC is going to be in the domain of the perigee. 
 
Total engagement of VIRK is the  second key event for onboard scientific payload functioning after deployment and fixation of the SRT antenna (July, 23d, 2011)!
 
•  August 13th
– a highly directive antenna pointing of a high informational channel
(VIRK) on the Pushchino TS antenna was  switched on. Within two hours the communication session with Pushchino TS  in mode loop of phase stability (LPS, a phase loop) was proceeded.
 
•  August 12th -- the spacecraft "Spectr-R" has passed a perigee on distance of 4000 km.
 
•  August 4th -- the spacecraft  "Spectr-R" has passed a perigee on distance of 2000 km from the Earth. The receiver and transmitter of PFS (this part of high informational radio channel (VIRK) is responsible for creation of a synchronization phase loop of TS and SC) was successfully switched on.
 
•  July 27th, 2011 -- after passage of shadow and a perigee the onboard H-maser was successfully turned on. 
 
•  July 26th, 2011 -- a procedure of onboard H-maser thermostats switching on preparation was done. 
 
•  July, 25th, 2011-- detenting of a VIRK sharp directional antenna drive is done. 
 
•  July, 23rd, 2011 -- deployment and fixation of the SRT antenna is done. 

http://www.asc.rssi.ru/radioastron/news/news_hot.pdf

Offline Salo

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Re: Russian Radioastron (Spectr-R) update
« Reply #2 on: 11/19/2011 08:47 AM »
News of the RadioAstron mission
by
Larisa Likhacheva, larlikh@asc.rssi.ru
Boris Novikov, nbs@mx.iki.rssi.ru
 
At present all systems and units of the SC "Spectr-R" work in a normal mode.
• Until August, 30th it was impossible to implement completely a highly stable signal of the onboard hydrogen maser due to the absence of synchronization by a signal of the hydrogen generator.
•  August, 31st  -- the command on switching on of  the second  onboard hydrogen maser has been given. The second hydrogen maser was switched on and from that moment it works stable and keeps all the specified parameters.
• At the same day (August 31st) for the functioning checking, all the scientific devices and units of the focal container have been switched on:  the shaper of heterodyne micro-wave frequencies, the micro-wave  signals selector, the block of pulse calibration, the control and analysis block (BUAS-F), four termostats of receivers on 18 and 92 cm. Also the part of instrumentation container devices was switched on. A successful switching on of  the rubidium standard of frequency (two complete sets
RUS01 and RUS02) produced by Neuchatel Observatory (Switzerland) also has been carried out. There are no remarks to the devices operation.

http://www.asc.rssi.ru/radioastron/news/news_hot.pdf
 

Offline Salo

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Re: Russian Radioastron (Spectr-R) update
« Reply #3 on: 11/19/2011 08:47 AM »
RadioAstron Newsletter
Number 5
September 16, 2011

Spectr-R in-orbit tests continue.
Many things have happened since the previous Newsletter which reported on the space radio telescope deployment.

Science payload and survice systems of Spectr-R weresuccessfully turned on. Technical details can be found here:
http://www.asc.rssi.ru/radioastron/news/news.html

In particular:
- The H-maser (atomic clock) was turned on and internal test has shown that the clock works properly, its stability is reported to be within the specs.
- Tests of "VIRK", the system which includes high-gain 1.5-m diameter antennae and is used to contact with the tracking station in Pushchino, continue. The so-called "open loop", the tone signal at 8 GHz, was successfully detected in Pushchino and is being used to perform Doppler measurements of the orbit parameters.

The 15 GHz tone signal was also successfully detected.
- Today, the first system temperature measurements were performed for the Australian-made 18 cm astronomical receiver while the space telescope was pointed on a cold sky;
the system temperature is estimated to be about 42 K which is close to receiver’s specifications.

Plans for the near future:
- VIRK pointing correction measurements and 15 GHz data link tests,
- performance measurements for all the other astronomical receivers of the 92, 6, and 1.3 cm bands,
- Cassiopea A first light single-dish radio astronomical observations including space radio telescope efficiency measurements.

With best regards,
Nikolai Kardashev (nkardash@asc.rssi.ru)
Yuri Kovalev (yyk@asc.rssi.ru)

http://www.asc.rssi.ru/radioastron/newsletter/newsl.pdf

Offline Salo

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Re: Russian Radioastron (Spectr-R) update
« Reply #4 on: 11/19/2011 08:48 AM »
http://www.engineeringnews.co.za/article/south-africa-set-to-join-space-radio-astronomy-programme-2011-09-23

"It is now almost certain that South Africa will soon join the Russian-led international Radioastron space telescope consortium. South Africa is expected to sign the agreement late this month or next month."

"South Africa is expected to use the new 15 m dish at the Hartebeesthoek Radio Astronomy Observatory (HartRAO), west of Pretoria, to participate in Radioastron. The 15 m dish was originally the XDM prototype dish for the Karoo Array Telescope (KAT, now MeerKAT) programme, but has been converted into an operational radio telescope to complement HartRAO’s main instrument, the 26 m dish."

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Re: Russian Radioastron (Spectr-R) update
« Reply #5 on: 11/19/2011 08:49 AM »
RadioAstron Newsletter
Number 6
September 27, 2011
======================
Russian version of the Newsletter can be found here:
http://www.asc.rssi.ru/radioastron/newsletter/newsl_rus.pdf
Spektr-R radiometers in the all four bands are functional The space radio telescope Spektr-R has on-board receivers covering four bands. First in-orbit receivers’ tests were completed recently. We are happy to report that radiometers in all the bands are functioning properly. Total system temperature values were measured and preliminary values are indicated below. These values are close to the specs and confirm high sensitivity at all the bands. Specifically:
* 92 cm (P) band total system temperature: about 200 K (made in: LNA - India, the rest of the receiver - Russia);
* 18 cm (L) band total system temperature: about 40 K (receiver made in Australia);
* 6 cm (C) band total system temperature: about 70 K (receiver made in Russia);
* 1.3 cm (K) band total system temperature: about 60 K at 22 GHz (made in: LNA - USA, the rest of the receiver - Russia).
The shown data are results of measurements performed in a single circular polarization for each receiver out of two polarization available.
More detailed performance measurements of the receivers and the space radio telescope as well as telescope pointing corrections, etc., at these four frequency bands are planned for the near future.

With best regards,
Nikolai Kardashev (nkardash@asc.rssi.ru)
Yuri Kovalev (yyk@asc.rssi.ru)

http://www.asc.rssi.ru/radioastron/newsletter/newsl.pdf

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Re: Russian Radioastron (Spectr-R) update
« Reply #6 on: 11/19/2011 09:06 AM »
RadioAstron Newsletter
Number 7
September 29, 2011
======================
Russian version of the Newsletter can be found here:
http://www.asc.rssi.ru/radioastron/newsletter/newsl_rus.pdf
Spectr-R space radio telescope first light!
On September 27, 2011, the first light from Cassiopeia A was detected with the space radio telescope Spektr-R of the Radioastron mission. The telescope scanned across the supernova remnant in two perpendicular directions. Signal in two bands of 92 and 18 cm (two circular polarization per band) was successfully detected in the total power mode. Enjoy the first light picture attached. The following space radio telescope key characteristics were preliminary determined:

92 cm:
effective area is 28 m^2 (pre-launch estimates on the ground: 25 m^2),
Full width at half maximum is 6.1 degrees (pre-launch: 6.1 degrees);

18 cm:
effective area is 46 m^2 (pre-launch estimates on the ground: 40 m^2),
Full width at half maximum is 72 angular minutes (pre-launch: 75’).

Next step -- 6 and 1.3 cm. Stay tuned.

With best regards,
Nikolai Kardashev (nkardash@asc.rssi.ru)
Yuri Kovalev (yyk@asc.rssi.ru)
To subscribe or un-subscribe to the Newsletter, use:
http://asc-lebedev.ru/index2.php?engdep=22

http://www.asc.rssi.ru/radioastron/newsletter/newsl.pdf
« Last Edit: 11/19/2011 09:08 AM by Salo »

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Re: Russian Radioastron (Spectr-R) update
« Reply #7 on: 11/19/2011 09:06 AM »
Astro Space Center
RadioAstron Newsletter
Number 8
November 3, 2011
======================

Space radio telescope tests in 6 and 1.35 cm bands Many observations of space objects have happened by Spektr-R in October 2011 in 6 and 1.35 cm bands. Cassiopeia A, Moon, Jupiter, as well as the Crab nebulae were observed in a scanning mode of a single radio telescopes. Radio signals from all these objects were successfully detected. The space radio telescope pointing has proven to be very good and stable. Tests at these two bands continue in order to achieve high quality telescope calibration information.

First maser observations by the space radio telescope

First single dish observations of a space object have happened on October 29 and 30 when scientific and telemetry data were transmitted to the ground through the wide band 15 GHz data link between Spektr-R and Pushchino tracking station. This mode of observations and recording is similar to the one which will be used for interferometric experiments. A maser source W3(OH) was observed in the OH (1665 MHz) and H20 (22232 MHz) lines. They correspond to 18 and 1.35 cm RadioAstron bands. The measurememnts have happened at the Spektr-R separation from the Earth by 60 and 200 thousand kilometers.
See attached figure with the spectra produced by the RadioAstron in-orbit checkout team of Astro Space Center.
W3(OH) is located about two kiloparsec away from the Earth in our Galaxy in a proto-stellar region. Radio emission from the object was collected by the 10-m space radio dish, digitized and formatted on-board, sent by the high-gain 1.5-m antenna to the Pushchino tracking station, decoded and recorded on the RadioAstron data recorder at the tracking station. Recorded data were transmitted to Astro Space Center over a dedicated Internet line. Data analysis in Astro Space Center confirmed the maser lines in both bands in left and right circular polarizations at expected frequencies, with expected amplitude and shape. As a result, this experiment has confirmed the full functionality of the space segment of interferometer.
First RadioAstron experiments in a mode of Space-Earth interferometer, so called fringe search, are planned to start in the second half of November 2011.

With best regards,
Nikolai Kardashev (nkardash@asc.rssi.ru)
Yuri Kovalev (yyk@asc.rssi.ru)

http://www.asc.rssi.ru/radioastron/news/news_en.pdf

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« Last Edit: 11/19/2011 09:33 AM by Salo »

Offline Salo

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Re: Russian Radioastron (Spectr-R) update
« Reply #9 on: 11/19/2011 12:17 PM »
http://www.plasma-f.cosmos.ru/en/content/interplanetary-shock-detected-by-bmsw-on-september-9-2011
Quote
Interplanetary shock detected by BMSW on September 9, 2011
31.10.2011

Interplanetary shock on September 9,  2011 was observed by Spektr-R as well as by SOHO, Wind and ACE spacecraft.

Graphs below show changes of the density and velocity direction as registered by BMSW in sweeping mode (compressed data):

These results as well as more information about BMSW had been presented at the workshop "Structure in the Solar-Wind Plasma", Ann Arbor, MI, USA, October 17-20, 2011.

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Re: Russian Radioastron (Spectr-R) update
« Reply #10 on: 11/19/2011 12:21 PM »
http://www.plasma-f.cosmos.ru/en/content/plasma-f-three-months-orbit
Quote
Plasma-F: Three months in orbit
18.11.2011

Dr. G.N. Zastenker, leading researcher, IKI RAS

Three months have passed since 'Plasma-F' payload aboard Russian astrophysical satellite SPECTR-R was switched on.

Among various phenomena, having occured during this period (August 08 – November 05), of particular interest was extremely sharp distrubance of solar wind which reached the Earth on September 9, 2011 and was registered by BMSW plasm spectrometer.

Read more
« Last Edit: 11/19/2011 12:27 PM by Salo »

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Re: Russian Radioastron (Spectr-R) update
« Reply #11 on: 11/24/2011 05:36 PM »
RadioAstron Newsletter Number 9
November 24, 2011

RadioAstron fringe search has started

First fringe search observations of the ground-space interferometer RadioAstron have started on November 15 and 23, 2011. Both sessions have happened successfuly, observations were made on the 18 cm band. Scientific data from the space radio telescope were successfully transmitted to and recorded by the Pushchino tracking station. The observations were supported by the following ground VLBI stations: three 32-m telescopes of the Russian VLBI network Kvazar in Svetloe, Zelenchukskaya, Badary, 70-m radio telescope in Evpatoria (Ukraine), 64-m Usuda (Japan), 100-m Effelsberg (Germany), 100-m GBT (USA). Quick data quality check has confirmed that the data are suitable for the fringe search. The data analysis center in Astro Space Center of Lebedev has started the interferometric fringe search.
The first RadioAstron fringe test on November 15 had been also supported by two EVN telescopes, Metsahovi 14 m (Finland) and Onsala 20 m (Sweden) as a part of the JIVE-led Planetary Radio Interferometry and Doppler Experiment (PRIDE). These PRIDE observations of the Spektr-R tone signal at 8.4 GHz will provide additional Doppler measurements for orbit determination feed into the data correlation process.
The RadioAstron team plans first fringe search experiments at the 6 cm band to happen in December 2011.

First successful distance measurements with a laser ranger

Laser ranging is one of several methods being used to reconstruct the Spektr-R orbit with high accuracy required for a proper functioning of the ground-space radio interferometer.
First successful laser ranging of Spektr-R has happened on November 15, 2011, from 5:30 to 6:30 Moscow time. The ranging was performed by the Observatoire de la Cote d'Azur (Grasse, France) as part of the International Laser Ranging Service. The distance measurements were done continuously during 35 minutes resulting in 875 independent measurements. The distance to the space craft has changed during this period of time from 65 to 70 thousand kilometers. Refelected signal was of a very high quality. The error of measurements is about or less than 10 cm.

Results are available from:
ftp://cddis.gsfc.nasa.gov/slr/data/npt_crd/radioastro/2011/

Pulsar PSR0329+54 and water maser Orion KL

As part of the ongoing in-orbit checkout activities, the brightpulsar PSR0329+54 was observed on November 7 at 316 MHz while the water maser in the Orion KL region -- on November 8, 2011, at 22 GHz. The space radio telescope scientific data were transmitted to the ground using the wide band data link to the Pushschino tracking station. Positive data processing results can be found on the attached plots indicating a good overall performance of the system.

With best regards,
Nikolai Kardashev (nkardash@asc.rssi.ru)
Yuri Kovalev (yyk@asc.rssi.ru)

http://www.asc.rssi.ru/radioastron/news/news_en.pdf

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Re: Russian RadioAstron (Spectr-R) update
« Reply #12 on: 12/08/2011 09:58 PM »
The RadioAstron Newsletter # 10, December 8, 2011.
http://www.asc.rssi.ru/radioastron/news/news_en.pdf

RadioAstron finds first interference fringes

We are delighted to report a successful detection of the first interference fringes -- a correlated signal on ground-to-space baselines -- by the RadioAstron team at the Astro Space Center of the Lebedev Physical Institure, Russian Academy of Sciences. The fringes were found between the space radio telescope, Spektr-R, and the following ground based radio telescopes: The 32-m Russian "Quasar" antennas at Svetloe, Zelenchukskaya, and Badary of the Institute of Applied Astronomy, Russian Academy of Sciences, the 64-m Ukranian antenna at Evpatoria, the State Space Agency of Ukraine, and the Max-Planck-Institute for Radio Astronomy 100-m antenna at Effelsberg, Germany. The observations of the quasar 0212+735 were made on November 15, 2011 at 18 cm wavelength. The attached picture shows the clear detection of the interference fringes on the baseline between Effelsberg and the space radio telescope on a delay-fringe frequency plot. The quasar 0212+735 was selected as a target by the Radioastron team on the basis of a preliminary determination of its very compact structure and high surface brightness by recent observations using the NRAO Very Long Baseline Array in the U.S.

The successful detection of interference fringes demonstrates the overall excellent status of the complex system and reflects the birth of the new international ground-to-space very long baseline interferometer, RadioAstron.

A search for fringes at other frequency bands and at longer interferometer baselines will continue until the end of January 2012, and will be followed by an "Early Science" program on quasars, AGN, pulsars, and cosmic masers. The Astro Space Center will also continue to perform in-orbit tests together with the Lavochkin Association including an effort to improve the quality of scientific data link from the space radio telescope to the ground through the Pushchino tracking station.

On behalf of the Astro Space Center, we would like to congratulate and thank the Lavochkin Association as well as the many other institutions in Russia, Ukraine, and other countries on their long lasting effort which resulted in this milestone result!

With best regards,
Nikolai Kardashev (nkardash@asc.rssi.ru)
Yuri Kovalev (yyk@asc.rssi.ru)
« Last Edit: 12/08/2011 10:01 PM by Salo »

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Re: Russian RadioAstron (Spectr-R) update
« Reply #13 on: 12/23/2011 09:37 PM »
RadioAstron Newsletter Number 11
December 23, 2011
http://www.asc.rssi.ru/radioastron/news/news_en.pdf

First interference fringe at 6 cm!

According to the RadioAstron in-orbit checkout plan, first interferometric observations at 6 cm were performed on December 1, 2011.
The target was chosen to be the bright, compact and distant active galaxy BL Lacertae. The correlated interference signal was immidiately found by the Astro Space Center RadioAstron correlator with a high signal-to-noise ration between the space and all ground radio telescopes, namely, Eupatoria (Ukraine), Effelsberg (Germany), Medicina (Italy), Yebes (Spain). See fringe examples in the attachement. The successful detection of interference fringes demonstrates the overall excellent status of the complex system at the 6 cm band and reflects the rediness of RadioAstron to start early science observations.

We are pleased to report that ground-space interference fringes at 18 cm were also found in our experiment on November 23 with all participating telescopes which include the 100-meter GBT (NRAO, USA) and 64-meter Usuda (JAXA, Japan) together with the Russian and Ukranian VLBI stations.

A quick success at both 18 and 6 cm bands allowed teh RadioAstron team to start science observations earlier than planned originally. Five SVLBI observing sessions were performed between December 10 and 14 on the extragalactic target BL Lacertae at 18 and 6 cm. Observations of this active galactic nucleus were done for baseline projections from several to more than 20 Earth diameters. The ground VLBI support was provided by the Quasar network, Eupatoria, Yebes, Medicina, Effelsberg. An extra interest is determined by the fact that BL Lacerta went in December 2011 through a major flaring event in radio. Analysis of these observations should allow for a significant step towards better understanding of physical processes in the core of this galaxy.

Giant pulses from the Crab pulsar

The RadioAstron network of the space and ground telescopes has observed gian pulses from the Crab pulsar on November 15, 2011. This experiment was performed in order to check synchronization accuracy of the space and ground time. The Crab pulsar emits so called giant pulses which are thousand times more luminous than its regular pulses. These giant pulses were successfuly detected at 18 cm at the space (Spektr-R) as well as ground (Quasar network, Eupatoria) radio telescopes. Scientists have successfully cross-identified giant pulses at all these telescopes. They matched with an accuracy about or better than one microsecond. This indicates a high reliability of the time synchronizaton between the space and ground telescopes. See figure of one of gian pulses detected by RadioAstron attached.

With best greeting to the New Year 2012!
Nikolai Kardashev (nkardash@asc.rssi.ru)
Yuri Kovalev (yyk@asc.rssi.ru)

P.S. Astro Space Center is very happy to congratulate academician Nikolai Kardashev with the award of the 2012 Grote Reber Gold Medal for innovative and significant contributions to radio astronomy.
http://www.qvmag.tas.gov.au/?articleID=539

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Re: Russian RadioAstron (Spectr-R) update
« Reply #14 on: 01/28/2012 11:22 AM »

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Re: Russian RadioAstron (Spectr-R) update
« Reply #15 on: 03/13/2012 02:49 PM »
The first results of Plasma-F experiment (only Russian):
http://www.plasma-f.cosmos.ru/first-results

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Re: Russian RadioAstron (Spectr-R) update
« Reply #16 on: 03/13/2012 02:51 PM »
http://www.novosti-kosmonavtiki.ru/phpBB2/viewtopic.php?p=899320#899320
Coogle translate:
Quote from: Vladimir  March 01, 2012 19:19
Today, held the second of the planned correction of the orbit. As in the first case (21 February), everything went normally. Time adjustment of the engine was 333 seconds (February 21 - 300 seconds). Total momentum is ~ 3.5 m / s.
  More on yesterday's meeting LOCT scientists reported that they were able to correlate the terrestrial and space observation of January 25. To obtain valid scientific results will take another month. The news, of course, is good, but the rate of  :-\

Medicina VLBI telescope observing calendar:
http://www.ira.inaf.it/Observations/calpar.htm
« Last Edit: 03/13/2012 03:05 PM by Salo »

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Re: Russian RadioAstron (Spectr-R) update
« Reply #17 on: 03/13/2012 03:14 PM »

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Re: Russian RadioAstron (Spectr-R) update
« Reply #18 on: 03/20/2012 07:11 PM »
The RadioAstron Newsletter # 12, March 20, 2012.
http://www.asc.rssi.ru/radioastron/news/news_en.pdf

Astro Space Center
RadioAstron Newsletter
Number 12
March 20, 2012

First 92 cm RadioAstron interference fringe at the 220,000 km baseline
projection!

On January 25, 2012, RadioAstron has successfully detected the first interferometric signal at 92 cm from individual pulses of the pulsar B0950+08 from the longest distance to the space craft - 300,000 km. Projected interferometer baseline was 220,000 km which provided the
highest ever achieved resolution at this wave length of about 1/1000 arcsecond. The ground VLBI stations which participated in this experiment are Arecibo (USA), Westerbork (the Netherlands), and Effelsberg (Germany). The interference fringes were found between the space radio telescope and all thee ground telescopes. See some result on the two attached figures.

The observed variations of the correlated signal from the pulsar is due to the propagation effects - pulsar emission scintillation on the inhomogeneous interstellar plasma. Such effect is only seen for emission of very compact objects. Thus, astronomers have got a tool to study characteristics of the interstellar medium and the pulsar itself, to localize the pulsar radiation zone in the magnetosphere of the neutron star - either above the polar cap or near the light cylinder. The conducted experiment has both confirmed RadioAstron capabilities at 92 cm and provided first important scientific data in this band. About 10 brightest radio pulsars of our Galaxy are planned to be studied in the RadioAstron early science program.

Tests of the closed-loop mode of Spektr-R synchronization

A test in a special closed-loop mode of Spektr-R synchronization was successfully performed on January 22, 2012. This mode of operation utilizes the ground based maser clock located at the Pushchino tracking station to synchronize the space radio telescope observations through a special up-down phase link at 7.2 and 8.4 GHz. As a result of these observations at 18 cm, an interference fringe was found by the RadioAstron correlator from the quasar 0212+735 at the projected distance of about 16,000 km.

Successful Spektr-R orbit correction

In order to correct the orbit of Spektr-R, two injections were done on February 22 and March 1, 2012, with a total momentum of about 3 m/sec.
The correction was performed successfully. As a result, the perigee of the space craft orbit has increased to about 55,000 km, the ballistic life time of the orbit has increased to 10 years.
The RadioAstron early science program and final steps of the fringe search Regular experiments within the RadioAstron early science program (ESP) have started in February 2012. Hydroxyl and water masers in our Galaxy (W3OH, Orion KL, etc.), the Crab pulsar as well as bright active galactic nuclei were observed since then. These experiments were supported from the ground by more than ten different VLBI stations: the European VLBI Network telescopes including the Russian ones, the Ukrainian Eupatoria, the Japanese Usuda. The international RadioAstron ESP working groups are reducing and analyzing the data together with the Astro Space Center correlator.
The fringe search experiments are finishing. First segments of 1.3 cm observations have failed due to very bad weather conditions on the ground (GBT, Effelsberg). The search for 1.3 cm fringes continues. Additionally, first test experiments with the Australian VLBI network LBA were performed on March 11, 2012, to prepare for science observations with LBA preliminary planned for May.

With best regards,
Nikolai Kardashev (nkardash@asc.rssi.ru)
Yuri Kovalev (yyk@asc.rssi.ru)

Offline Salo Ukr

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Re: Russian RadioAstron (Spectr-R) update
« Reply #19 on: 06/14/2012 01:42 PM »
http://www.asc.rssi.ru/radioastron/news/news_en.pdf

Astro Space Center
RadioAstron Newsletter
Number 13
June 14, 2012
======================

First RadioAstron 1.3 cm fringes!

Along with conducting the RadioAstron Early Science Program, the RadioAstron fringe search team continued interferometric tests at 1.3 cm (K-band) -- the shortest RadioAstron wave length. We are happy to report that the first K-band fringes were successfully detected on a baseline Spektr-R -- Effelsberg (MPIfR, Germany) from the compact quasar 2013+370. Moreover, these observations were organized in a dual-band mode. Simultaneous measurements at 6 cm were carried out on the baseline Spektr-R -- Westerbork (WSRT, the Netherlands). The 6 cm fringes were found on this baseline with delay and rate values which agree to the 1.3 cm results. The attached Figure shows the 6 and 1.3 cm fringes. The baseline projection was 1/4 of the Earth diameter.
This positive result marks the successful end of in-orbit tests of the ground-space radio interferometer RadioAstron.

RadioAstron coherence time

Coherence time in radio interferometry is the maximum time interval for which the interferometric signal can be coherently (without loses) integrated. Sensitivity of interferometric measurements is proportional to the square-root of this value. Typical coherence time of ground-ground very long baseline interferometric experiments is 1 to 15 minutes for centimerter wave lengths; it is determined by characteristics of the turbulent atmosphere, ionosphere, troposphere.
Coherence time analysis is extremely important since it characterizes the overall sensitivity as well as stability of the system, including atomic clock.

We have perfomed an analysis of the RadioAstron coherence time at the shortest wave lengths, 6 and 1.3 cm, using observations from March 15 and May 12, 2012, consequently, on the baseline Spektr-R -- Effelsberg. Results are shown on the Figure attached. The signal-to-noise ratio increases as a square-root of integration time (fringe fitting interval) up to about 10 minutes at 6 cm and up to 2 minutes at 1.3 cm. This first estimate of the coherence time demonstrates high stability of the space element of the RadioAstron interferometer.

RadioAstron International Science Council meeting 2012

The RadioAstron International Science Council (RISC) will meet for several days in Pushchino, Moscow region, starting from June 18, 2012. The main goal of the meeting is to discuss the current status of the mission and plans for organization of future RadioAstron experiments. The meeting will unite representatives of Russian and International institutions including many major radio observatories of the world.

With best regards,
Nikolai Kardashev (nkardash@asc.rssi.ru)
Yuri Kovalev (yyk@asc.rssi.ru)

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« Last Edit: 06/14/2012 01:48 PM by Salo Ukr »

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