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

Two 26 Meter Radio Telescopes for Long-Term
Monitoring Programs and Surveys
Not-for-profit
public
foundation
www.pari.edu
J. D.
1PARI; 2Summer
Introduction
1
Cline ,
M. W.
1
Castelaz ,
Research Student at PARI;
A.
3Webb
2,3
Castelaz
Institute of Naval Architecture
Session 49.04 Tuesday, January 11, 2005. AAS 205th Meeting
26 East Antenna
26 West Antenna
The New Control System
Two 26 m radio telescopes on a 300 m
nearly east-west baseline
Pointing Models
Procedure for Pointing Model
Pointing Models Correct for
• 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
• 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
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
TMAJ,EMAJ all points
0.5
0.4
0.3
0.2
EMAJ error
Pisgah Astronomical Research Institute is a not-forprofit public foundation located on 200 acres in Western
North Carolina in the Pisgah National Forest.
0.1
Series1
0
-100
-50
Linear (Series1)
-0.1 0
50
100
Poly. (Series1)
EMAJ vs. TMAJ
Curve = tube flexure for major axis = 0.036
Slope = major axis scale factor = 23.76 arcsec
-0.2
-0.3
y = 0.0069x + 0.011
R2 = 0.9265
-0.4
-0.5
TMAJ obs
y = 5E-06x 2 + 0.0068x + 0.0066
R2 = 0.9272
TMAJ,EMIN all points
0
-100
-50
0
50
100
-0.2
EMIN error
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
Series1
-0.4
Linear (Series1)
-0.6
Poly. (Series1)
Scale factor and nearly zero flexure for major axis
EMIN vs. TMAJ
Curve = elevation misalignment in = 0.144
Slope = azimuth misalignment in = -10.08 arcsec
-0.8
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:
•
•
•
•
•
See http://www.pari.edu/ for more information
Equatorial and
GalacticCoordinates
Time
Telescope Status
User Catalog
Weather
TMAJ obs
Current Research
TMIN,EMAJ all points
Pulsars
0.5
0.4
0.3
• Dr. David Moffett, Furman University, PI.
EMAJ error
0.2
0.1
0
-60
-40
-20
-0.1 0
20
40
Series1
Linear (Series1)
Poly. (Series1)
-0.3
-0.4
• 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.
Major axis azimuthal and elevation corrections are small
EMAJ vs. TMIN
Curve = collimation = 0.144
Slope = non- perpendicularity of the axes = -2.88
-0.2
-0.5
y = -4E-05x2 - 0.001x + 0.0057
2
R = 0.0111
TMIN obs
Little correction is needed for collimation and for nonperpendicularity of the major and minor axes.
TMIN,EMIN all points
0
-60
-40
-20
0
20
40
-0.2
EMIN error
Major
Axis
Minor
Axis
• 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.
y = 2E-05x 2 - 0.0019x - 0.6292
R2 = 0.1502
-1
-0.4
Series1
Linear (Series1)
-0.6
-0.8
-1
TMIN obs
Poly. (Series1)
y = 0.0034x - 0.5871
R2 = 0.2529
y = -4E-05x 2 + 0.003x - 0.5694
R2 = 0.2664
EMIN vs. TMIN
Curve = tube flexure for minor axis = -0.360
Slope = minor scale factor = 15.48 arcsec
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
New Research Initiative
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.
FeedBox Infrastructure
26 E Feedbox
26 W Feedbox
Feedboxes have AC power, coax,
fiber and appropriate cabling as
required by receiver configuration.