ARM Enhanced Shortwave Experiment (ARESE)
September 25 - November 1, 1995
Standard Operating Procedure for UMass 95 GHz Bar
I. Introduction
This manual serves to outline the standard operating procedures followed by the University of Massachusettes researchers when operating the 95 Ghz radar. It contains description of the system, set-up procedures, operation of the instrument, and potential hazards.
II. System Description
A. Overall System
The 95 Ghz radar is scanning pulsed Doppler radar. Short duration pulses of millimeter-wave radiation are transmitted in order to make high resolution measurements of clouds. It utilites a four-foot parabolic reflector to produce a narrow beam. The radar is mounted on a mechanical positioner to allow scanning.
System Specifications:
Transmit frequency 94.93 GHz
pulse width 50 2000 no
prf 200 Hz - 20 kHz
duty cycle .5%
peakpower 1.5kW
average power 7.5 W
beam width 0.2 deg.
B. AC Power
The system requires power supplied by the experiment site. The system uses one single-phase 220 VAC 60 Amp line and either one or two (as available) 120 VAC 15 Amp lines. Grounding is achieved by attaching the electrical ground of the circuit breaker to a grounding rod.
C. Physical Layout
The 95 GHz radar is carried in and operated from a 32' long, 8' wide diesel truck. The instrument will be mounted on a platform up to 20 feet from the truck in order to allow a clear scanning path. A four meter radius cattle fence around the radar platform will prevents person and cattle from approaching the radar. A 12' long by 7' high compartment on the forward portion of the truck's bed houses all of the data acquisition and control equipment. The platform on the back of the truck is surrounded by a chain fence to prevent unauthorized personnel from climbing onto the truck and to prevent personnel from falling off the truck. There are two entrances to the work area of the truck: a side door and a rear overhead door. The side door has steel stairs with a handrail. The rear door leads to theplatfom on the back of the truck.
III Set-up procedures
Set-up of the system requires approximately one day. Two people are required for most of the set-up, but four or five people are required for some tasks.
A. Positioning the truck
The truck will be located at the central facility of the CART site. The truck must be parked on a compacted surface which is generally flat and level. Four leveling jacks can be used to level the truck, and these jacks are lowered onto four 2' X 2' steel plates. The chassis of the truck is strapped to the ground to provide greater stability.
B. Electrical setup
Pror to electrical set-up all electrical equipment is disconnected. If a grounding rod is not available at the site, one is hammered into the ground. The equipment ground is then attached to the grounding rod. A 60 Amp cable is plugged into a 220 V outlet provided by the site. Voltages at all outlets are checked with a digital voltmeter. Once it is confirmed that all voltages are correct, equipment can be plugged in.
Prior to doing any electrical work on the radar or truck, the equipment on which the work is being performed is disconnected or the circuit is broken at the circuit breaker.
C. System set-up (radar and calibration tower)
The UMass team will arrive approximately one week prior to the start date of the ARESE experiment and leave one or two days after the end of the experiment.
After unpacking the hardware from the truck the radar and antenna are mounted on the positioner. All heavy objects are moved by two or more people, and the lift gate on the back of the truck is used to lift objects onto the back of the truck.
Most of the electronic equipment is mounted in two racks inside the truck. A table is provided for the computer terminals, and a work bench is positioned at the front of the cube section for other work.
The 95 Ghz radar also uses a corner reflector mounted on a 40’ tower in order to calibrate the system. Erection of the tower requires four or five people. The tower is assembled horizontally on the ground, and then it is tilted upright. The tower is secured with guy wires. The tower should be located 600 to 800 meters away from the radar.
10. Personnel
Two UMass people will participate in the experiment. The radar can be operated with only one person present. Both people in the UMass research team will be capable of operating the instrument by themselves.
IV. Data taking procedures (including operation times)
The UMass radar will be operated during all times when the ARESE aircraft are flying. The radar may also be operated during times when the ARESE aircraft are not flying. These additional operations will occur between 0-24hrs depending on cloud conditions.
The radar is capable of being operated in different modes. The radar can be operated in an upward- looking mode, a scanning mode, or a calibration mode. The system is periodically scanned down near the horizon and pointed at a corner reflector for calibration. A readout on the positioner controller and a video camera mounted on the antenna give the the pointing direction of the antenna so that the operator knows where the beam is pointed at all times.
During normal operations, all persons operating the radar will be within the shielded portion of the truck. While the radar is transmitting, all personnel are prohibited from being within four meters of the antenna bore-sight, and at least one person must be monitoring the radar. When the transmitter is in stand-by, the system may be left unattended.
V. Potential Hazards
The 95 Ghz radar transmits non-ionizing radiation. Because the system is pulsed the average power is relatively low, and the microwave hazards are small. The safe distance from the antenna beam has been calculated to be 4 meters in the direction of maximun intensity, which is directly on the axis of the antennna beam. The walls of the truck have been shielded to protect the operators, and warning signs are posted outside the truck.
The transmitter uses high voltage to generate the microwave pulses. A sign is placed on the radar to warn of the presence of high voltage. The high voltage cables are enclosed inside the radar box where they can not be accidently touched. High voltage is only present while the radar is transmitting, and at that time no one is allowed near the radar as previously mentioned.
A soldering station is located on the workbench in the truck. A fan in the back of the truck is used to provide proper ventilation
For all hazardous chemicals brought onto the site there are accompanying material safety data sheets. These are included in the SOP and filed with site personnel.
Contact: Ray Bambha
