Bobby L. Ulich

Planetary observations at a wavelength of 1. 32 mm

Observations at a wavelength of 1.32 mm have been made of the Jovian planets, Ceres, the satellites Callisto and Ganymede, and the HII region DR 21. The observed brightness temperatures are presented. Those of the Jovian planets agree with the values expected from model atmosphere calculations, except that of Jupiter, which is lower than expected. Ceres and the satellites do not have atmospheres so their emission arised in their subsurface layers. The observed brightness temperatures are intermediate between those measured at infrared and centimeter wavelengths.

Planetary observations at a wavelenght of 355 μm

Abstract Observations at a wavelenght of 355-μm have been obtained for the giant planets Jupiter, Saturn, Uranus, and Neptune, for the Galilean satellites Europa, Ganymede, and Callisto, and for the asteroid Ceres. The brightness temperatures for the different objects are 145 ± 18 for Jupiter, 134 ± 21 for Saturn, 69 ±8 for Uranus, 69 ± 9 for Neptune, 148 ± 31 for Europa, 114 ± 9.5 for Ganymede, 135 ± 11 for Callisto, and 117 (± 10) for Ceres.

SEEING MEASUREMENTS ON MOUNT GRAHAM

A transportable 30-cm aperture telescope was constructed and used with a CCD camera to measure stellar image motion as seen from the summit of Mount Graham in southeastern Arizona. Based on observations during eight nights in October and November 1984, the average value of Frieds length r0 (Fried, 1967) at 0.5 micron wavelength is 13 cm at the zenith, implying a long-exposure visual image full width at half maximum of 0.8 arc second. Since only a small number of nights have been tested, the statistical uncertainty in the average seeing conditions is large and these results should be regarded as preliminary. No large differences were found among three different sites or between different heights of the telescope above the ground. Direct measurements of thermal turbulence in the first few tens of meters above ground indicate that telescopes may be located within a few meters of the ground and well below treetop height without significant seeing degradation.

A New Surface Measuring Technique Using Phase Retrieval By Amplitude Interferometry

A new surface measuring instrument has been developed which is capable of measuring surface errors to the submicron level. RMS noise in measuring the surface error was found to decrease as [integration time]-1/2. The instrument can measure surface errors to within 10 microns in a small test region in only a few seconds of integration. The instrument could therefore be used to align radio telescope panels to high precision in real time.

MMT Pointing And Tracking

The Multiple Mirror Telescope exhibits good tracking performance and excellent pointing accuracy. Considerable engineering effort has been expended over the past four years to investigate methods for improving accuracy, and to identify and understand the sources of the remaining errors. We can achieve tracking errors as low as 0.5 arcseconds peak-to-peak without autoguiding, and RMS pointing errors better than 1 arcsecond, but changes of approach may be needed to reach our tracking performance goals.

A 26-Bit Absolute Encoder System

In October, 1985, new encoder readout electronics were installed on the MMT to read the existing absolute encoders. With the new electronics, the angular resolution of the encoder system has been increased from 24 bits (0.077 arcseconds) to 26 bits (0.019 arcseconds) and the amplitudes of the raw uncorrected errors related to the period of the InductosynsTM* have been reduced from a few arcseconds to the order of +/- 0.5 arcseconds or better.

Low-Cost Enclosure For The Sub-Millimeter Telescope

The University of Arizona and the Max-Planck-Institut fur Radioastronomie are collaborating to construct a sub-millimeter wavelength radio telescope facility at the summit of Mt. Lemmon (2791 m above sea level) near Tucson, Arizona. We have designed a corotating building to protect the 10 m diameter Sub-Millimeter Telescope (SMT) against storm damage, to provide large instrumentation rooms at the Nasmyth foci, and to minimize degradation of the reflector profile accuracy and pointing errors caused by wind forces and solar radiation.