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Absrmcz-Siace its development inthe l W s , the tedmique of obtaining-resohrtionmdioimagesofastmaomrcsl * ubjedslsiagFourier synthesishpsadvaacedsuffii~soth.ttodayarhimrgesoftenp* betterrrngulprresdutioo~isobbineMedthehrgestopticnltde-r o p e s A~~. a r r a y m e t n s p s t h e F o u i e r t~a~u f o r m o f t J~e o b s e R e d brightwss-byaosscorrehtingthesigndsfromant~sep mated by dbtamxs up to tens of kilometers. Tbe antennas must be p b p f e -s t . b l etiuks wide-bradrsidth digital CoITeMOrs B1p usedtoperformtheeros~mdrtaredpctioatllgorithmsd complrtingsystemplayacritialroleindeterminiagthequnlityofthe imnses pmdueed by m y . ~verYLprge~Y(vLA)sYn~~descope,recently-~ esllipped nith low-wise receiviag systens d together by . . in New Mexico, comisb of twenty-seven S m d i a m e t e r antennas uranged i n a Y -s b . p e d~y . E r b s r m o f t h e Y i s~~~2 1 L m l o n g a n d the antemas can be moved to various positiolrs on the arms by a mil-mounted trnmporter. m mteeluns sre equip@ d cryogenicrlly coded receiving q s t e m s and are i n t -e d by low-los, TE, , -mode, 5o.MHzbrndnidthctigit.lcorrelrtor. Inthisprperwedisamthefk?signofspthesisaITaysingewraland d e r r i b e t h e d e s i g n d p e r f o n M n c e o f t h e V W i n p u t i c u l n r , l m d e r t h e seven headings array geometq design, sensitivity phase s t r b i l i t y w n t s s i g n r l t system, del.Y and -o r system,coatrolsystem,anddotr-redrrtionrequirementr.Ineachsectioa, w e r e~t h e~i n s h u m e n t d r e q o i r e m e n t s d p v i d e d e t a i k o f tiondgodmtspvideeffdvewaysofawrectingspthesisimagesfor t l~e e f f e c t s o f~F w i e r~t s d i n s t r u m e o t n l a n d~ l a r g e -d i . m e t e r w a v e g u i d e . T b e~~f o r e a r b o f t h e 3 5 1 p r k c o m b i n l b i o m o f s n t e n n a s a r e~f o r 4 I F s i g n r l s b y a. . h o~t h e V L 4~~d e s i g n e d t O m e e t t h e m , R~~d e~~d r c p r e d u csphericamplitudeandphaseemKsTbepowerofthesePlgorithmsis demodmtedusil?gshlnlvLAiD1.pff T I. hTRODUCTION HE INCREASE in the performance of radio telescopes from the late 1940's through the present time has led notonly to the discovery of many thousands of radio sources but, more importantly, to a spectacular increase in our appreciation of the nature and variety of objects in the astronomical universe. An essential element in this progress has been the ability to compare the observed features of objects over a wide spectral range; the radio, infrared, visible, ultraviolet, and X-ray domains. Because of the enormous number of detectable objects, particularly in the visible range, accurate position measurements are essential to enable a source detected in one spectral domain Radio Astrmomy Observatory -0)is operated by Associated Universi-

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In almost 30 years of operation, the Very Large Array (VLA) has proved to be a remarkably flexible and productive radio telescope. However, the basic capabilities of the VLA have changed little since it was designed. A major expansion utilizing modern technology is currently underway to improve the capabilities of the VLA by at least an order of magnitude in both sensitivity and in frequency coverage. The primary elements of the Expanded Very Large Array (EVLA) project include new or upgraded receivers for continuous frequency coverage from 1 to 50 GHz, new local oscillator, intermediate frequency, and wide bandwidth data transmission systems to carry signals with 16 GHz total bandwidth from each antenna, and a new digital correlator with the capability to process this bandwidth with an unprecedented number of frequency channels for an imaging array. Also included are a new monitor and control system and new software that will provide telescope ease of use. Scheduled for completion in 2012, the EVLA will provide the world research community with a flexible, powerful, general-purpose telescope to address current and future astronomical issues.Comment: Added journal reference: published in Proceedings of the IEEE, Special Issue on Advances in Radio Astronomy, August 2009, vol. 97, No. 8, 1448-1462 Six figures, one tabl

A 12 m diameter radio telescope will be deployed to the Summit Station in Greenland to provide direct confirmation of a Super Massive Black Hole (SMBH) by observing its shadow image in the active galaxy M87. The telescope (Greenland Telescope: GLT) is to become one of the Very Long Baseline Interferometry (VLBI) stations at sub-millimeter (submm) regime, providing the longest baseline >9000 km to achieve an exceptional angular resolution of 20 μas at 350 GHz, which will enable us to resolve the shadow size of~40 μas. The triangle with the longest baselines formed by the GLT, the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, and the Submillimeter Array (SMA) in Hawaii will play a key role for the M87 observations. We have been working on the image simulations based on realistic conditions for a better understanding of the possible observed images. In parallel, retrofitting of the telescope and the site developments are in progress. Based on 3 years of opacity monitoring at 225 GHz, our measurements indicate that the site is excellent for submm observations, comparable to the ALMA site. The GLT is also expected to make single-dish observations up to 1.5 THz.