... They are concerned with Attitude Control System of the spacecraft, satellite visibility from tracking stations, limits on the satellite autonomous operations during the orbit, and needs for auxiliary operations with the spacecraft. ... Among the operational constraints the most important one is the number of programmed slews per orbit, which determines the maximum number of radio sources to be observed during one orbit. ... System temperature (K) . ... Progress of the RadioAstron Project in Pictures...

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Weekly Bulletin on Solar and Geomagnetic Activity Highlights on 06 - 12.04.2015, Forecast on 13 - 20.04.2015, Carrington Rotation 2162 (27,93.03.2015) SUNSPOT-FORMING ACTIVITY OF THE SUN WAS AT THE AVERAGE LEVEL ALL DAYS. ... BY DATA OF CORONOGRAPHS SOHO AND STEREO WERE OBSERVED > 38 CME FROM WHICH FOUR WERE "PARTIAL HALO II" TYPE. ... R - solar rotations; KP - KIT PEAK solar observatory; EE-date of possible geomag. disturbance in the Earth's environment. ...

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... Frequency of wobble same as frequency of forcing mechanism (t) + i 2 (t) · Helmholtz Centre Potsdam ­ GFZ · Consistent estimates of AAM , OAM , HAM computed at GFZ · AAM computed from European Centre for Medium-Range Weather Forecasts · OAM computed from Ocean Model for Circulation and Tides (OMCT) · HAM computed from Land-Surface Discharge Model (LSDM) · Ocean and hydrology Sensitivity to Excitation Model GFZ ECMWF AAM OMCT OAM LSDM HAM 1962­2010 1971­2010 1981­2010 1991­2010 2001­2010! ...

... This limited extent suggests that the currents which disturb the field flow somewhere nearby, probably near the auroral arcs. ... Any electric current, however, must flow in a closed circuit, and since it seemed to be caused (like that of the aurora) by processes taking place in distant space, Birkeland proposed that it came down from space at one end of the arc and returned to space at the other end. ... The electric energy needed to drive the current is taken from the motion, which is slowed down....

... Our Sun is part of a huge wheel-shaped collection of stars. ... Astronomers have long suspected it was a very massive black hole, and that every galaxy had such a central mass, created early in the history of the universe. ... However, unless that object happens to be headed directly at the black hole (a relatively small target) it will just swing around and fly away again, like a comet making a pass at the Sun. The velocity acquired in falling towards the black hole also helps it escape. ...

... The choice of the spectrograph design (Fig.2) is determined by the quantity R, the overall dimensions of the PF cage and the restrictions on the rigidity of the structure of the device. ... As the camera's objective a fast 4-lens aplanat is used having a focal distance F cam =140 mm and a relative aperture of 1:1.8, the resolution at the centre is no less than 80 gr/mm, that over the field at a distance of 3 mm from the edge along the frame ( ) diagonal is 35 gr/mm. ...

... Uniformity of size and appearance of all the illustrations of the same type should be strictly observed. ... The numbers of curves, straight lines, etc., should be written in italics without any brackets both at an illustration and in text. ... In inscriptions, when the parameters of a curve are listed, the numbers of curves and notations of the parts of an illustration (a, b, etc.) should be placed in brackets prior to the corresponding parameters (a dash is not used). ...

... A1368 Date Received: 1999-Oct-04 10:06:54 Technical Page Proposal Type: Regular General Category: Astronomy Sub-Category: Spectroscopy Observation Category: Extragalactic Total Time Requested: 20 hr Hours Proposal Title: PKS1004+13: The Rosetta Stone for BAL Quasars? ABSTRACT: It is now recognized that the material producing broad absorption lines (BAL) in some quasars is in fact present in essentially all such objects, only orientation restricting the observed occurrences to 15%. ...

... International Space Station in Transit . ... But while Wednesday's leisurely transit of Mercury across the Sun entertained observers all over the dayside of planet Earth, the audience for this lunar transit was more restricted. ... Can you spot the planet? The diminutive disk of Mercury, the solar system's innermost planet, spent about five hours crossing in front of the enormous solar disk yesterday (Wednesday, May 7th), as viewed from the general vicinity of planet Earth. ... Galaxies.. ...

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Next: Rotation Periods of ZAMS stars Previous: T Tauri Stars . ... The first attempts to directly measure periodic modulation of T Tauri stars occurred in the early 1980s. Rydgren & Vrba (1983) observed four PMS stars using photoelectric photometry over a period of seven consecutive photometric nights. ... Because the spot lifetime is much longer than the rotational period, the observed effect will be a modulation of the light from the star synchronously with the rotation period. ...

Astronomers at Armagh Observatory observed the partial eclipse of the Sun on 29 March under unusually good conditions. ... The images, taken by astronomer Miruna Popescu, shows the eclipse as seen from the Armagh Observatory at around 11:30 (Summer Time) on 29th March, and the way it was observed by astronomer Apostolos Christou with a small portable telescope equipped with a filter to protect against the Sun's dangerous radiation. ... For more images from Armagh see: Miruna Popescu's Pages . ...

... Following the full moon on Monday, March 24, I was able to make use of a few brief periods totalling about an hour and a half before the Easter weekend to make some 160 galaxy observations at home in Coonabarabran using the 0.41m telescope. ... Because of being on holidays my resources for comparison purpouses were rather limited, and so I had to rely upon amateur contacts in Queensland to verify my memory of this galaxy, and also to obtain visual confirmation of the supernova. ...

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Next: Retrieving demonstration and Up: Echelle Reduction Method Previous: Echelle Reduction Method . ... User data is a set of echelle images, observed with the same instrument configuration, including a wavelength calibration image ( WLC ), a flat field image ( FLAT ) and astronomical objects OBJ . Optionally, this set will include standard stars ( STD ) to be used in the absolute or relative flux calibration, and dark images ( DARK ). ... Rotation of input frames. ...

... Star Atlas . ... Behemoth black hole found in an unlikely place . ... black holes . ... First black holes kept to a strict diet, study shows . ... This frame from the simulation shows the X-rays produced by a black hole (white) and its effects on nearby gas (blue). ... For the first time, we were able to simulate in detail what happens to the gas around those stars before and after they form black holes." ... Yet, despite its strict diet, the black hole had a dramatic effect on its surroundings. ...

RTT150 . ... The primary mirror 1 reflects light to the secondary mirror 2 which sends the converging beam of light to the system of four flat mirrors 3, 4, 5 and 6. That allows the beam of light to leave the telescope strictly along its polar axis and be collected in Coude focus. ... That's why at any tube position (for any rotation along the declination axis) beam of light parallel to the principal axis after reflection on mirror 3 follows the direction of declination axis. ...