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ATA Antennas Feeds and Systems

ATA Antennas Feeds and Systems. NSF Review 8/05/08 Jack Welch. The Allen Telescope Array of 350 dishes in Northern CA ~ 2010. Array of a Large Number of Small Dishes (LNSD). A Survey Telescope with large field of View

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ATA Antennas Feeds and Systems

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  1. ATA Antennas Feeds and Systems NSF Review 8/05/08 Jack Welch

  2. The Allen Telescope Array of 350 dishes in Northern CA ~ 2010

  3. Array of a Large Number of Small Dishes (LNSD) • A Survey Telescope with large field of View • For Multiple Pointings, point source sensitivity is proportional to ND, not NDD • Single Wide Band Feed insures frequency agility • Complementary to other cm wave telescopes • US Pathfinder for the SKA mid-band

  4. A “Green Telescope” • All ambient antenna heating and cooling is done by underground air flow

  5. ATA - 350 Dishes Made By TVRO Companies 6m primary Radome Shroud Log-periodic Feed with Actuator 2.4m secondary

  6. 6m Antenna Optics • Offset Gregorian - Unblocked Aperture • Higher Gain • Lower sidelobes -15db • Shroud lowers spillover and background noise and interference • Total surface RMS=.7mm • Wide field of View: 3degrees at 1 GHz • Aperture efficiency > 0.6

  7. The Antenna Pattern At 2.3 GHz

  8. Dewar/Cryo 12” Refrigerator Dewar LNAs

  9. Wideband Feed (Log Periodic) • Range: 0.5 – 11 GHz • Input reflection < -15 db • LNA within dewar at 62K • Cryocooler inside the feed • Feed gain 11.5 db +/- 1 db • Feed f/D = .65 • All receiver electronics a part of the feed • Entire analog band sent to lab in fibers • Dual linear polarization

  10. Overall System • Four RF Downconverters produce 600 MHz Dual Polarized Bands at Any Input Frequency • Filters feed 100 MHz bands to backends • AD Converters (8 bit) drive Spectral Correlators and beamformers • Simultaneous SETI and other astronomy Observing Enabled • Good Overall gain Stability for Single Antenna Observations of Large Scale Structure

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