Two 26 Meter Radio Telescopes for Long-Term Monitoring Programs and Surveys

1. Two 26 Meter Radio Telescopes for Long-Term Monitoring Programs and Surveys Not-for-profit public foundationwww.pari.edu J. D. Cline1, M. W. Castelaz1, A. Castelaz2,31PARI; 2Summer Research Student at PARI; 3Webb Institute of Naval Architecture Introduction Session 49.04 Tuesday, January 11, 2005. AAS 205th Meeting • The 26 m radio telescopes • Installed by NASA for the Gemini and Apollo programs. • In excellent condition because of rigorous and consistent periodic maintenance since that time. • Motion controls have been upgraded for astronomical use. • This poster presents • The new control system • The pointing models • FeedBox infrastructure support • Current research • New research initiative Pisgah Astronomical Research Institute is a not-for-profit public foundation located on 200 acres in Western North Carolina in the Pisgah National Forest. Pointing Models • Pointing Models Correct for • Non-perpendicularity of radio axis to minor axis • Non-perpendicularity of minor to major axes • Elevation misalignment in both axes • Azimuth misalignment in both axes • Encoder eccentricity and phase angle • Tube flexure in both axes • Procedure for Pointing Model • Point the telescope at radio point sources throughout the sky and record observed Major and Minor axis positions. • Difference Observed and Catalog Positions. • Plot differences with catalog positions. • Fit the plots with second order polynomials – coefficients are pointing model parameters 26 East Antenna 26 West Antenna EMIN = difference between Minor axis observed and catalog position EMAJ = difference between Major axis observed and catalog position TMIN = Minor Axis Observed Position TMAJ =Major Axis Observed Position EMAJ vs. TMAJ Curve = tube flexure for major axis = 0.036 Slope = major axis scale factor = 23.76 arcsec Scale factor and nearly zero flexure for major axis Two 26 m radio telescopes on a 300 m nearly east-west baseline EMIN vs. TMAJ Curve = elevation misalignment in = 0.144 Slope = azimuth misalignment in = -10.08 arcsec The New Control System Major axis azimuthal and elevation corrections are small • Each telescope follows an alt-alt coordinate system. • The major axis moves the telescope East-West. • The minor axis moves the telescope North-South. • DFM Engineering telescope control system. • Installed on 26 East antenna in 2001 and 26 West antenna in 2002. Current Research EMAJ vs. TMIN Curve = collimation = 0.144 Slope = non- perpendicularity of the axes = -2.88 • Pulsars • Dr. David Moffett, Furman University, PI. • 327 MHz receiver installed on 26 East antenna. • Timings of a dozen pulsars. • Methanol Maser Survey • Dr. Mel Blake, PARI, PI. • 6.7 GHz receiver installed on 26 West antenna. • Unbiased single-dish survey of northern hemisphere sky. • Currently in the process of receiver calibration. Little correction is needed for collimation and for non-perpendicularity of the major and minor axes. Minor Axis EMIN vs. TMIN Curve = tube flexure for minor axis = -0.360 Slope = minor scale factor = 15.48 arcsec Major Axis Scale factor and correction for flexure of the minor axis Using the models, both telescopes now Point to within 2 arcminutes and Track to better than within 1 arcminute per hour • Control of both antenna are linked to a central computer which • Controls the telescopes separately or as a common pair. • Drives a telescope in raster scan mode for mapping. • Allows user-defined catalogs. • Uses either Equatorial or Galactic coordinates. • Define track rates. • Telecontrol on the central computer. Features standard telescope control items including: • Equatorial and GalacticCoordinates • Time • Telescope Status • User Catalog • Weather New Research Initiative FeedBox Infrastructure • Extreme Scattering Events (ESEs) and Intra-Day Variables (IDVs). Brian Dennison, UNC-Asheville, PI. • Long-term monitoring of interstellar turbulence via its effect on scattering of radio waves over a large sample of compact sources. • Two element interferometer to reduce noise confusion and measure point sources. • Two frequencies, 2.4 GHz and 8.4 GHz. 26 E Feedbox 26 W Feedbox Feedboxes have AC power, coax, fiber and appropriate cabling as required by receiver configuration. See http://www.pari.edu/ for more information