[Doc Ewen looks into the horn antenna, 1950]
Image courtesy of Doc Ewen


Harvard Cyclotron: 1948-1951

Detection of HI Line: 1951

Harvard 24ft and 60ft and NRAO founding: 1952-1956

1950s and 1960s: Two Roads that Crossed

Microwave & Millimeter Wave Applications in the 1970s and 1980s

Mm Wave Radiometry in the 1990s

May 2001 visit to NRAO Green Bank



[Doc Ewen and horn antenna, 2001]
Image courtesy of Doc Ewen

Doc Ewen: The Horn, HI, and Other Events in US Radio Astronomy

by Doc Ewen, © 2003

Slide presentation: Millimeter-Wave Radiometry in the 1990s

Section 2: RAVIN-SL5 95 GHz 5 ft Aperture Radio Telescope


Purpose: The RAVIN-SL5 telescope meets the need for data concerning the millimeter wave characteristics of man-made and natural phenomena. Phenomenology measurement capabilities include: the millimeter wave radiation characteristics of rocket plumes during the launch phase, millimeter wave characteristics of destructive kinetic energy events, cloud polarization phenomena, and the millimeter wave imaging of stealth surfaces against the cold radiation background of the sea and sky.

Implementation: The design and assembly of the RAVIN-SL5 telescope was based on capabilities and equipment developed by AFRL/MNGS during the past decade under the STAG program. The plan and product of the STAG sensor development program is shown in the slides. The RAVIN-SL5 telescope combines the RAVIN 50 foot low bed trailer equipment facility with a World War II 5 foot search light equiped with the RF head of a ROSCAM Airborne Imaging millimeter wave camera. The moon is used for focusing and calibration, as an optical.radio target conveniently located at all observing sites of interest. Integration of the search light antenna with the RAVIN platform, and enhancement of the antenna drive system, was provided by the Millivision Corporation.


Search light: The antenna is a World War II seach light with a 5 foot aperture. The unit was completely disassembled, refurbished, and reassembled. The original drive system was removed, with the exception of the DC motors and gear trains. A solid state drive system is now incorporated in the system to provide the minimum 10 degree per second slew rate needed to track most objects of interest. THere are no angle encoders at present. Target tracking is based on operator use of a TV display derived from an optical camera co-boresighted with the radio boresight.

RAVIN trailer: The mobile platform is a 50 foot low bed trailer equiped with a 25 foot truck body which has been refurbished with 3 windows, a rear door, and a front door entrance via an air lock to minimize temperature changes in the main equipment room. Counter-top benches are integrated into the structure on either side of the room. The telescope control console is located across the rear 8 feet of the room, in front of the rear door, and extends 3 feet into the room. The control panel includes the drive controls for the antenna, TV screen display along the radio boresight, with zoom control down to 6 x 6 , TV screen display of the antenna as seen from a camera mounted on the wireless weather station directly over the front door, Stagecam radiometer control panel with a signal meter and zero and gain control pots, VCRs for recording both the view of the antenna and the target, event clocks that provide a count down and count up display, temperature calibration unit controls with selection of ambient temperature, target temperature, or automatic cycle between ambient and target, Brush 220 dual channel high speed strip chart with dual channel event markers, Omega single channel strip chart, and the wireless weather station monitor panel.

Radiometric sensor: The sensor is a modified ROSCAM airborn imager. The ROSCAM is a superhet with a single-ended mixer input operating at the fundamental frequency of 95 GHz. The frequency band of the two stage IF is 1-4 GHz. The detected output is fed to a video amplifier which drives the 75 foot cable connecting the RF head and the control unit. The nominal system noise temperature is 1000K. In combination with the predetection bandwidth of the IF chain, the ROSCAM provides a sensitivity of ‹ 1K rms for a post detection integration time constant of 0.1 millisecond.

Click on the thumbnails for larger photos and fuller explanations.

Slide 1: RAVIN-SL5 at Millivision.
Slide 2: RAVIN interior.
Slide 3: RAVIN interior.
Slide 4: RAVIN control panel.
Slide 5: Moon drift scan.
Slide 6: RAVIN-SL5 at Westover.
Slide 7: Temperature calibration unit.

Modified on Tuesday, 14-Jun-2005 08:50:48 EDT by Ellen Bouton