Author Topic: Russian RadioAstron (Spectr-R) update  (Read 44249 times)

Offline Salo

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Re: Russian RadioAstron (Spectr-R) update
« Reply #60 on: 12/21/2016 04:16 PM »
http://www.asc.rssi.ru/radioastron/ao-5/ao5.html
RadioAstron Announcement of Opportunity - 5

 The space VLBI Mission RadioAstron, led by the Astro Space Center (ASC) of Lebedev Physical Institute, provides a range of specific and unique capabilities for detecting and imaging sources of cosmic radio emission at the highest angular resolution. The optimal utilization of these capabilities relies on the construction and execution of a balanced scientific program for the Mission. Proposals are invited for the RadioAstron Key Science Program and General Observing Time experiments to be submitted by 23 January 2017, 23:59 UT, to the Mission, and to ground radio telescopes required for the specific observations by their respective proposal deadlines. AO-5 observations will be performed between July 2017 and June 2018 inclusive.
 Proposals are to be submitted by e-mail as single pdf files to the address: ra_submit@asc.rssi.ru

 List of AO-5 related documents

- The RadioAstron Announcement of Opportunity - 5;
- The RadioAstron User Handbook;
- Full Proposal template: LaTeX file and pdf file;
- All-sky uv-coverage simulations with Pushchino and Green Bank tracking stations: pdf file;
- ASCII table with RadioAstron AO-5 visibility prediction for selected targets from the RadioAstron list of observed sources;
- Fakerat full binary package (is tested to work with most Linux distributions) including installation README, manual, and predicted RadioAstron AO5 orbit prior to the maneuver planned for 2017-07-16 and after it (ASCII files);
- All documents collected togeter in a zip-file
- RadioAstron observations status summary. Acknowledgment for the project publications

 To subscribe to RadioAstron Newsletter click here
« Last Edit: 12/21/2016 04:34 PM by Salo »

Offline Salo

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Re: Russian RadioAstron (Spectr-R) update
« Reply #61 on: 03/15/2017 04:09 PM »
http://www.asc.rssi.ru/radioastron/news/newsl/en/newsl_31_en.pdf
======================
Astro Space Center
RadioAstron Newsletter
Number 31
15 March 2017
======================

The RadioAstron AO-5 open science program: July 2017 – June 2018

The  RadioAstron  observations  currently  cover  the  fourth  year  of  the  open  program  within  the approved AO-4 proposals.  Starting from July 2017, the RadioAstron mission will move into the fifth year of its program, AO-5 observations will continue until June 2018.  We note that an orbit correction is planned for July 2017 which will affect the RadioAstron observing schedule in July and  August  2017.   The  fifth  RadioAstron  Announcement  of  Opportunity  has  invited  proposals of the following two types:  the “Key Science Program” (KSP) and “General Observing Time” (GOT).  See  for  details  the  full  set  of  announcement  documents  in http://www.asc.rssi.ru/radioastron/ao-5/ao5.html .
All proposal were evaluated by the RadioAstron Program Evaluation Committee (RPEC) which was appointed by the RadioAstron International Science Council (RISC). Results of the evaluation were approved by the RadioAstron project director Nikolai Kardashev.  RPEC members for AO-5 are Jason Hessels (U. Amsterdam, the Netherlands), David Jauncey (CSIRO, Australia), Matthew Lister (Purdue U., USA), Alexander Pushkarev (CrAO, Russia), Mark Reid (chair, Harvard CfA, USA), Olaf Wucknitz (MPIfR, Germany). Below we list 11 accepted projects which have requested observations with RadioAstron during the AO-5 period in their submission order:

• GOT: “Visibility tracking of hyper-compact H2O maser spots for studying interstellar microturbulence”, PIs:  Hiroshi Imai (Kagoshima U., Japan), Alexey Alakoz (ASC Lebedev, Russia);
• GOT: “Monitoring of substructure in scattering disk of pulsar radio emission”, PI: Carl Gwinn (UCSB, USA);
• GOT: “Brightest objects in the distant Universe”, PI: Leonid Gurvits (JIVE and TU Delft, the Netherlands);
• KSP: “Evolution of high brightness temperature AGN cores with RadioAstron”, PI: Yuri Kovalev (ASC Lebedev, Russia);
• KSP:  “Probing  the  innermost  regions  of  AGN  jets  and  their  magnetic  fields”,  PI:  Jose-Luis Gomez (IAA, Spain);
• GOT: “Probing interstellar scattering material using dense RadioAstron observations of refractive substructure in AGN”, PI: Mikhail Lisakov (ASC Lebedev, Russia);
• GOT: “Observations of the central maser regions in H2O megamaser NGC4258 with ultimate angular resolution”, PI: Willem Baan (ASTRON, the Netherlans).
• GOT: “Early stages of massive star formation regions as seen with RadioAstron in H2O maser lines”, PI: Stan Kurtz (UNAM, Mexico);
• KSP: “Gravitational redshift experiment with RadioAstron”, PI: Valentin Rudenko (SAI MSU, Russia);
• KSP:  “The  nuclear  structure  in  M87  with  RadioAstron”,  PI:  Tuomas  Savolainen  (Aalto  U., Finland; MPIfR, Germany);
• GOT: “Resolving the gamma-ray production region in sources J0211+1051 and S5 1044+71”, PI: Victor Patino-Alvares (MPIfR, Germany).

Among the approved projects, six got rank ‘A’ (the highest priority).  A total of more than 160 co-investigators represent 20 countries.  The largest number of co-Is are from Russia, other countries with a high number of co-investigators include the USA, Germany, Spain, the Netherlands, Australia, Canada.

The absolute record of angular resolution by RadioAstron. Again.

While the readers are welcome to enjoy recent RadioAstron publications
( http://www.asc.rssi.ru/radioastron/publications/publ.html ), we are happy to announce a new absolute record of the angular resolution which was achieved detecting the megamaser in NGC 4258 at 1.3 cm on the
RadioAstron Space Radio Telescope to Medicina (Italy) baseline of 340,000 kilometers (26.7 Earth diameters,  8 μas).  The previous record of 11 μas on the same megamaser by the RadioAstron SRT to the GBT baseline was announced during the EVN symposium in Sankt-Petersburg.
In the same time, within a dedicated experiment on the glorious pair of the quasars 3C 273 and 3C 279, a very compact core was detected in 3C 279 at 1.3 cm by the SRT to the Jansky VLA baseline of 235,000 kilometers (18.5 Earth diameters, 12 μas).
These results are crucial to probe the physics of both the water vapor megamasers and the extremely bright and compact cores of quasars.

Nikolai Kardashev (nkardash@asc.rssi.ru)
Yuri Kovalev (yyk@asc.rssi.ru)

Offline Olaf

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Re: Russian RadioAstron (Spectr-R) update
« Reply #62 on: 07/16/2017 03:10 PM »
https://www.roscosmos.ru/23770/
bing translation
On 16 July, in 9:00, the Lavochkin NGO PCO made a correction to the orbit of the spectrum-R spacecraft, provided to prevent the spacecraft from being hit in January 2018 by a long (4.5 hour) solar shadow of the earth and extending the ballistic existence of spacecraft at least until the end of 2019.

The highly elliptical orbit of the spectrum-R is characterized by a significant evolution of parameters through the influence of the moon, is the so-called "evolving" orbit, which, on the one hand, enhances the possibilities of scientific observation, on the other, requires careful monitoring and prediction of its behaviour.

A similar correction was made successfully in March 2012. Due to the long interruption in the use of the adjustment engines one month prior to the nominal adjustment, on 16 June, a test correction was carried out by Lavochkin NGO specialists to confirm that the major correction engines worked in the staff and there was no need to use reserve engines. The impulse of the trial correction was less than at the nominal rate when engine time was 290.3 seconds.

A feature of the spacecraft correction was that they were carried out without interruption of the scientific program. The test adjustment practically did not change the orbit of the spacecraft, and the results of the nominal correction were previously taken into account by scientists in the establishment of the open scientific programme of the Space Astrophysical Observatory for the Spectrum-R for 2017-2018 years.

The Spectrum-R spacecraft has been developed in the NGO Lavochkin and is the space component of the international project of Astronomy. The project is implemented by the Astro Space Physical Institute Centre. P.N. Lebedev of the Russian Academy of Sciences, together with other institutions of the wounds and organizations of the State Corporation for space activities.

The purpose of the project is to carry out basic astrophysical research in the electromagnetic spectrum. Observations are made through terrestrial radio telescopes (more than 40) and the Spectrum-R Orbital Observatory. Together they form a radio interferometer with a, base, which allows you to get images of distant objects in the universe with an unparalleled angular resolution fixed at 8 microseconds of the arc.

The Spectrum-R spacecraft and the design of the radio telescope have been developed by Lavochkin NGOs. A unique telescope antenna with a diameter of 10 meters is made of composite material and consists of 27 drop blades and a central mirror of 3 meters. The apparatus is the largest space radio telescope in the world!


           

Offline Salo

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Re: Russian RadioAstron (Spectr-R) update
« Reply #63 on: 11/20/2017 04:27 PM »
http://www.asc.rssi.ru/radioastron/news/newsl/en/newsl_32_en.pdf
======================
Astro Space Center
RadioAstron Newsletter
Number 32
27 July 2017
======================

Successful Spektr-R orbit correction

The planned orbit correction of the Spektr-R space craft was successfully performed by the Lavochkin Association on 16 July 2017 at 06:00 UT. The total impulse was equal to 1.6 m/s, accuracy 2 %.  As a result, the corrected orbit is very close to its predicted values.  The correction was made in order to avoid an excessively long shadow and a too low perigee in the first half of 2018.  The planned science program continues to the full extent. We congratulate colleagues with the 6th anniversary of the launch!

Nikolai Kardashev (nkardash@asc.rssi.ru)
Yuri Kovalev (yyk@asc.rssi.ru)

The RadioAstron project is led by the Astro Space Center of the Lebedev Physical Institute of the Russian Academy of Sciences and the Lavochkin Scientific and Production Association under a contract with the Russian Federal Space Agency, in collaboration with partner organizations in Russia and other countries.

Offline Salo

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Re: Russian RadioAstron (Spectr-R) update
« Reply #64 on: 11/20/2017 04:38 PM »
http://www.asc.rssi.ru/radioastron/news/newsl/en/newsl_33_en.pdf
======================
Astro Space Center
RadioAstron Newsletter
Number 33
20 November 2017
======================

RadioAstron has switched to a backup synchronization mode

The hydrogen maser onboard the RadioAstron space Radio Telescope has finished its operations in July 2017 after six years of perfect performance, due to the exhaustion of its neutral hydrogen. This was consistent with its expected lifetime.
The RadioAstron science and technical operations working group has performed a number of checks  of  two  other  methods  of  synchronization:  one  utilizing  the  onboard  rubidium  standard, and  the  other  being  the  so-called  closed–loop  mode  of  operations.   The  latter  uses  the  ground atomic clock located in Pushchino (Russia) or Green Bank (USA) tracking station.  Both modes have  successfully  delivered  interferometric  fringes.   At  the  same  time,  best  results  are  achieved with the closed–loop mode, as expected.  This mode of synchronization is being used right now as the default for observations in the AO5 science program.
RadioAstron AO6 proposals will be due by January 22, 2018 for observations from July 2018 – June 2019.  An announcement of the proposal call will be made in the near future.

Testing Einstein’s general relativity

The RadioAstron Key Science Program on the gravitational redshift experiment has completed its data collection stage. The observations for the experiment were supported by EVN, NRAO, and several geodetic radio telescopes (Badary-Russia, Effelsberg-Germany, GBT-USA, Hartebeesthoek-South Africa, Onsala-Sweden, Svetloe-Russia, VLBA-USA, Wettzell-Germany, Yarragadee-Australia, Yebes-Spain,  Zelenchukskaya-Russia).  The goal of the project is to test Einstein’s Equivalence Principle  — the  basis  of  general  relativity.  Specifically,  the  team aims  to  verify  Einstein’s  formula for the gravitational redshift effect or, equivalently, the gravitational time dilation due to a nearby massive body.  For the RadioAstron spacecraft the effect due to the Earth is about − 58 microseconds per day relative to an observer at the Earth’s surface — time actually flows faster
aboard  the  spacecraft  hence  the  minus  sign. The  most accurate test of this kind to date was performed  in  1976  by  the  NASA-SAO  Gravity  Probe  A  mission.   That  experiment  proved  the validity of Einstein’s formula with an accuracy of about 0.01 % using a suborbital probe equipped with  a  hydrogen  maser  frequency  standard.   The  experiment  with  RadioAstron  is  based  on  a similar approach, depicted in Figure 1, but benefitted from a better performing hydrogen maser and  a favorable  highly  eccentric  orbit,  which  allowed  the  team  to  perform  their  measurements team believe they’ll be able to supersede the result of their renowned predecessor by an order of magnitude.  This anticipated result will mark an important milestone in our challenge to find the level at which general relativity breaks down and a more general theory, such as string theory, is beginning to reveal its subtle features.  The team have recently published a paper (Litvinov et al. https://doi.org/10.1016/j.physleta.2017.09.014 ), presenting their techniques and giving a status update of the experiment.  Figure 2 illustrates the results of preliminary data processing of one of the experiments.  While the data processing is far from finished, the currently achieved accuracy is already at the level of that of Gravity Probe A.

Nikolai Kardashev (nkardash@asc.rssi.ru)
Yuri Kovalev (yyk@asc.rssi.ru)

The RadioAstron project is led by the Astro Space Center of the Lebedev Physical Institute of the Russian Academy of Sciences and the Lavochkin Scientific and Production Association under a contract with the Russian Federal Space Agency, in collaboration with partner organizations in Russia and other countries.

To subscribe or un-subscribe to the Newsletter, use: http://asc-lebedev.ru/index2.php?engdep=22


Offline Salo

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Re: Russian RadioAstron (Spectr-R) update
« Reply #65 on: 11/20/2017 04:57 PM »
http://www.sciencedirect.com/science/article/pii/S0375960117304553?via%3Dihub
Probing the gravitational redshift with an Earth-orbiting satellite
Author links open overlay panel D.A.Litvinov V. N.Rudenko A.V.Alakoz U.Bach N.Bartele A.V.Belonenko K.G.Belousov M.Bietenholze A.V.Biriukov R.Carmang G.Cimóh C.Courde D.Dirkx D.A.Duev A.I.Filetkin G.Granato L.I.Gurvitsh A.V.Gusev …M.V.Zakhvatkin
https://doi.org/10.1016/j.physleta.2017.09.014
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Abstract

We present an approach to testing the gravitational redshift effect using the RadioAstron satellite. The experiment is based on a modification of the Gravity Probe A scheme of nonrelativistic Doppler compensation and benefits from the highly eccentric orbit and ultra-stable atomic hydrogen maser frequency standard of the RadioAstron satellite. Using the presented techniques we expect to reach an accuracy of the gravitational redshift test of order 10-5, a magnitude better than that of Gravity Probe A. Data processing is ongoing, our preliminary results agree with the validity of the Einstein Equivalence Principle.
« Last Edit: 11/20/2017 05:02 PM by Salo »

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