FW: RadioAstron Newsletter 13
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From: <Chris.Phillips_at_email.protected>
Date: Mon, 18 Jun 2012 09:57:59 +1000
>
>________________________________________
>From: Yuri Y. Kovalev [yyk_at_asc.<!--nospam-->rssi.ru]
>Sent: Thursday, June 14, 2012 9:10 PM
>Subject: RadioAstron Newsletter 13
>
>Astro Space Center
>RadioAstron Newsletter
>Number 13
>June 14, 2012
>Russian version of the Newsletter can be found attached and here:
>http://www.asc.rssi.ru/radioastron/news/news_ru.pdf
>
>
>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 centimeter 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 performed 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_at_asc.<!--nospam-->rssi.ru)
>Yuri Kovalev (yyk_at_asc.<!--nospam-->rssi.ru)
>
>
>
Received on 2012-06-18 09:59:01
Date: Mon, 18 Jun 2012 09:57:59 +1000
>
>________________________________________
>From: Yuri Y. Kovalev [yyk_at_asc.<!--nospam-->rssi.ru]
>Sent: Thursday, June 14, 2012 9:10 PM
>Subject: RadioAstron Newsletter 13
>
>Astro Space Center
>RadioAstron Newsletter
>Number 13
>June 14, 2012
>Russian version of the Newsletter can be found attached and here:
>http://www.asc.rssi.ru/radioastron/news/news_ru.pdf
>
>
>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 centimeter 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 performed 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_at_asc.<!--nospam-->rssi.ru)
>Yuri Kovalev (yyk_at_asc.<!--nospam-->rssi.ru)
>
>
>
Received on 2012-06-18 09:59:01