The technical characteristics of the Atmospheric Sciences Research Facility, the improvements being made to the instrumentation there which will enhance its usefulness in atmospheric research, and several of the on-going research programs are described. Among the area of atmospheric research discussed are clouds and precipitation, lightning, ozone, wind, and storms. Meteorological instruments including Doppler radar, spectrophotometers, and ozone sensors are mentioned. Atmospheric research relevant to aircraft design and COMSTAR communication satellites is briefly discussed

Carr, R. E.

Gerlach, J. C.

English

NASA Technical Reports Server

.. FACILITIES FOR METEOROLOGICAL RESEARCH
AT THE NASA GODDARD/WALLOPS FLIGHT FACILITY
John C. Gerlach and Robert E. Carr
National Aeronautics and Space Administration
Goddard Space Flight Center/Wallops Flight Facility
Wallops Island, Virginia
(HASA-TM-84422) f ACUITIES FOE
METEOROLOGICAL BESEARCJ3 AT N A S A
GODDABD/HALLOPS FLIGHT FACILITY
Beport (NASA) 6 p HC A02/MP A01
Final
CSCL Q*4B
G3/47
N84-25223
Unclas
19377
Preprint from: Fifth Symposium on Meteorological
Observations and Instrumentation
April 11-15, 1983
' Toronto, Ontario, Canada
https://ntrs.nasa.gov/search.jsp?R=19840017155 2020-03-20T21:55:00+00:00Z
ORIGINAL
OF POOR FACILITIES FOR METEOROLOGICAL RESEARCH
AT THE NASA GODDARD/WALLOPS FLIGHT FACILITY
John C. Gerlach and Robert E. Carr
National Aeronautics and Space Administration
Goddard Space Flight Center/Wallops Flight Facility
Wallops Island, Virginia
1. INTRODUCTION
The Wallops Flight Facility of the
NASA Goddard Space Flight Center has
established the Atmospheric Sciences
Research Facility (ASRF) to support the
development of a vigorous atmospheric
research program. This Facility is
built around two ultra-sensitive, high-
resolution, coherent radar systems, and
includes a Lightning Research Facility,
consisting of several different
lightning measurement instrumentation
systems; an Applied Physics Measurements
Laboratory, equipped with several
different ozone spectrophotometers, and
related instrumentation; and, an
Environmental Data Acquisition and
Recording System.
Wallops has other instrumentation
systems which are not part of ASRF, but
are frequently used to support investi-
gations conducted at ASRF. . .These
include other coherent radars,, a' radio-
sonde launch facility, .meteorology
rocket facilities, a. meteorological
forecast unit, a real-time display of
the National Weather Service WSR-57
radar located at NAS, Patuxent River,
and several aircraft on which instru-
ments can be mounted. A real-time video
display of satellite images should be
available by summer 1983.
This report describes the technical
characteristics of the Atmospheric
Sciences Research Facility, discusses
improvements being made to the instru-
mentation which will enhance its
usefulness in atmospheric research, and
describes several of the on-going
research programs. It also serves as an
introduction to the facility to
potential users and invites them to use
it for their own research.
2. ATMOSPHERIC SCIENCES RESEARCH
FACILITY
The ASRF consists of the Radar
Atmospheric Research Facility (RARF),
the Lightning Research Facility (LRF),
the Applied Physics Measurement
Laboratory (APML), and the Environmental
Data Acquisition and Recording System
(EDARS) . The Facility is fully
supported by data displays, data
handling equipment, data processing com-
puters, and operating personnel.
2.1 Radar Atmospheric Research Facility
(RARF)
The RARF consists of two separate
research and development radar systems.
One o p e r a t i n g in the UHF-band (70 cm)
and the o the r in the S-band (10 cm) .
The Faci l i ty was constructed in the late
1950's for a p r o g r a m invo lv ing atmos-
pher ic re-entry of missi le payloads.
Since 1965, the Facil i ty has been used
almost exclusively for atmospheric
research projects. Simultaneous
measurements in the UHF- and S-bands can
be made of clouds and precipitat ion to
deduce particle size and characteristics
including quantitive cross sections of
individual hailstones and raindrops.
Relative attenuation at these wave-
lengths can be used to calculate path-
integrated r a in fa l l and water content.
-(Cox & Masterson, 1969)
The S-band radar , called the Space
Range Rada r ( S P A N D A R ) , has two trans-
mitters: A high-power t ransmitter wi th
a peak power output of 5.0 megawatts and
a low-power transmitter wi th a peak
power of 1.3 megawatts. Both have a 10
MHz bandwidth over a f requency band of
2700 to 2900 M H z . For m e t e o r o l o g i c a l
measurements both t ransmi t te rs are
controlled by a frequency d i v e r s i f i e r .
The d ive r s i f i e r shif ts the t ransmit
f r e q u e n c y of each r ada r pulse by the
reciprocal of the pulse width , thus
making each pulse independent in
frequency f rom every other pulse.
Frequency diversi ty allows for the
accumulation of a large number of inde-
pendent meteorological echoes at a much
faster rate than normal; it rejects
second-time-around targets, and it
inserts a cal ibrat ion signal for
receiver d r i f t compensation.
The r e tu rn signal is stored on tape
and is displayed in real- t ime on color
v ideo m o n i t o r s . The d i s p l a y can be
ei ther a Plan Posit ion Indica tor ( P P I )
or a Range Height Ind ica tor ( R H I ) . The
r ange n o r m a l i z e d r e f l e c t i v i t y i s con-
toured into six separate color levels.
An A i r c r a f t Pos i t ion Indica tor ( A P I ) '
places the pos i t ion of an a i r c r a f t ,
being t racked by another r ada r , on the
PPI as a f l a sh ing dot. The d isp lays can
be remoted to any si te which can receive
standard WSR weather radar da ta .
ORIGtNAL PAGE BS
OF POOR QUALITY
A color graphics computer is being
integrated into the system for use in
1983. This will provide for multiple
displays, such as PPI scans and RHI
scans, as well as doppler mean veloci-
ties and spectral variance whenever
doppler processors are attached to the
system.
At the moment, RARF does not have a
doppler processor. In the past, any
group who used the radar supplied their
own real-time doppler data processor.
Wallops is planning to add a permanent
doppler capability to the radar by CY
1984.
In addition to the incorporation of
the color graphics system and the
upgrading of the radar for doppler
processing, the radar computer system is
being replaced with a Data General
Eclipse S-130 microcomputer. This will
greatly increase the data collection and
analysis capabilities of the radar.
The UHF radar is a coherent, wide
bandwidth, high-power, 70 cm wavelength
radar with peak transmitter powers of
over 6 MW and a bandwidth adjustable up
to 50 MHz. The broad bandwidth allows
the radar to take pulse-to-pulse and
pulse-shape data. 'The coherent output
allows for doppler velocity measurements
to be made. The long wavelength makes
the radar ideally suited to detect
lightning channels without :.: serious
attenuation from rain along the beam
path.
The received signal from the UHF
radar can be displayed and recorded only
by using the SPANDAR data processing
electronics. Therefore, simultaneous
display or recording from both radars is
not possible. As the SPANDAR data
recording system is upgraded, the
existing system will be dedicated to the
UHF.
This past summer, the UHF radar was
used to locate regions of lightning in
real-time. The radar energy reflected
from the ionized channel was recorded on
video and analog tape for study and
analysis.
The technical characteristics of
the RARF radars are given in Table 1.
2.2 Lightning Research Facility
The Lightning Research Facility
(LRF) consists of four lightning detec-
tion and-measurement systems. Three of
these systems detect and measure the RF
radiation emitted from an electrical
discharge and the fourth senses the
change in the magnetic field due to the
electrical discharge. These systems are
the Lightning Detection and Ranging
(LDAR) System (Poehler & Lennon, 1979);
TABLE 1
Relevant Parameters of
the RARF Radars
SPANDAR UHF
Frequency
(MHz)
Peak Power
Output (MW)
2700 to 2900
1.0 or 5.0
420 to 450
-1.0 to 6.0
Minimum
Detectable
Reflectivity
or Cross Section
Per Unit Volume _._
at 10 km(cm~ ) 10
Pulse Length
(Microseconds) 1, 2, or 5 0.1 to 6.0
Beam Width
(Degrees)
Sensitivity
(db)
0.39
-119
2.9
-112
the Goddard/Georgia Tech Sferics Data
System (LeVine & Krider, 1977); the
Lightning Location and Protection (LLP)
System (Krider, et al, 1980); and the
Ryan Stormscope.
The LDAR was originally developed
at NASA Kennedy Space Center to detect
potential hazardous electrical activity
that might impair space launch opera-
tion. Wallops acquired it in 1979 and
put it into operation in 1981.
LDAR measures the times of arrival
of the pulsed RF radiation emitted by an
electrical discharge. This RF radiation
is detected by VHF antennas at outlying
sites and relayed to a central station
where the spatial location of the dis-
charge is determined. This signal is
recorded on digital tape and the raw
data on analog tape. The location of
source of RF signals is plotted on both
a PPI display and an RHI display. The
position accuracy within 15 km of ASRF
is better than 1% (Poehler, 1978) and
decreases with increasing distance.
Quite usable data can be obtained for
distances as far as 110 nautical miles.
The Goddard/Georgia Tech Sferics
Data System measures the RF radiation
characteristics of lightning at
selectable wavelengths from 3 MHz to 300
MHz. Normally, wavelengths of 3 MHz, 30
MHz, 70 MHz, 139 MHz, and 295 MHz are
used. The system is capable of
measuring slow and fast electric field
changes generated by the lightning.
Vertically polarized radiation is
detected by vertical quarter-wave
ORIGINAL PAGE ig
OF POOR QUALITY
monopole antennas for each frequency
except 3 MHz where a base-loaded
monopole antenna is used. Horizontally
polarized radiation is detected by
resonant (half-wave) dipoles at 139 MHz
and 295 MHz. Electric field changes are
detected by a flat plate antenna. The
RF and electric field measurements are
recorded on magnetic tape for later
reduction. A chart paper recording
provides a real-time output.
For a more complete description of
the system, see LeVine & Krider (1977);
LeVine (1978); and LeVine (1980).
The LLP is a commercial direction
finding (DF) system designed to plot
locations of cloud-to-ground lightning
flashes within nominal ranges of 100,
200, or 400 kilometers. It requires two
or more antenna sites for triangulation.
The antennas are orthogonal loop
antennas which sense the magnetic field
of the lightning flash. The DF system
processes the data for each stroke and
transmits them to a position analyzer
(PA) which computes and maps the ground
stroke locations. The DF also displays
lightning times, angles, signal
strengths, and other characteristics of
the strokes. (Krider, et al, 1980)
Antenna sites are located at NASA
Wallops; NASA Langley Research Center,
about 80 nm southwest of Wallops; and,
the Naval Research Facility, Dahlgren,
Virginia, about 90 nm northwest of
Wallops. These three sites form a
point-to-point system which is embedded
within a larger multidrop system of the
State University of New York (SUNY) at
Albany. The multidrop system includes
sites in New Jersey, Pennsylvania, and
New York. Table 2 gives technical
specifications for the system.
The Ryan Stormscope is primarily
designed for use in an aircraft to
provide bearing and range information of
electrical discharges relative to the
aircraft. Radio frequency signals,
generated by electrical discharges, are
picked up by a single flat-pack antenna
which provides both the V and H direc-
tion loop antennas and an electrical
sense antenna. The system records and
displays up to 128 individual electrical
discharges as small green dots on the
CRT and automatically updates the
"oldest" discharge information with the
"newest."
For an evaluation of the
Stormscope, see Baum & Seymour (1979).
2.3 Atmospheric Physics
Measurements Laboratory
The Atmospheric Physics
Measurements Laboratory (APML) was
TABLE 2
LLP System
Range 100, 200, or 400 km.
Detector 90% of all flashes wi th in
E f f i c i e n c y range.
Angular 1 degree or better.
Accuracy
Unwanted Filters for 50 or 60 Hz.
Signal Shape reject ion of noise
Reject ion and out of range signals.
Mult ip le Up to 14 return strokes
Strokes per f lash.
Communica- Point-to-point, mul t id rop ,
tions or dial-up. (Selectable
baud rate up to 4800
baud . )
Outputs Analog X- and Y-axis
voltages: Time of dis-
charge (to 0.1 sec.).
Azimuth angle (to 0.1
Degree) : Signal Strength
- Number of return
strokes.
established in 1979 to support an inter-
comparison among several . d i f f e r e n t
spectrophotometers used to measure the
total ozone content in a column of the
atmosphere. (Parsons, et al, 1982A) As
now c o n f i g u r e d , the A P M L has a Dobson
spectrometer, a Canterberry f i l t e r
spectrophotometer, a Sentran f i l ter
photometer , and a NO sensor. Also
under development is a Michelson
in te r fe rence spectrometer which wil l
allow the measurement of atmospheric
constituents f rom the ultra-violet
through the near in f ra - red regions.
(Parsons, et al, 1982B)
2.4 Environmental Data
Acquis i t ion and Recording
System
EDARS is a g e n e r a l purpose data
acquisi t ion and recording system de-
signed to record data f rom environmental
sensors. EDARS presently collects data
f r o m two types of sensors; ozone sensors
and a w i n d da ta sys tem. The ozone
sensors are located at AMPL and the wind
data sensors are on the 300-foot
meteorological tower on Wallops Island.
The sys tem is d e s i g n e d to r eco rd da t a
f r o m up to 50 d i f f e r e n t sensors w i t h
input rates up to 1,000 parameters per
second.
Avai lab le data that can
in te r faced into the system inc lude:
1. Ozone data f r o m dasibi sensors.
2. Radiosonde da t a .
be
ORIGINAL PAGE SS
OF POOR QUALITY
3. Wind data from remoted sites.
4. Daily weather summaries.
5. NO chemical sensor data.
6. Hydrocarbons chemical sensor data.
7. Hourly weather observations.
8. ASRF support summaries.
3.0 ACTIVE PROGRAMS
Atmospheric research using these
facilities has been conducted at Wallops
since long before the establishment of
ASRF. From the early 1960's through
1977, the Air Force Cambridge Research
Laboratory and the Applied Physics
Laboratory of Johns Hopkins University
used the radars for investigations of
clear air turbulence, insect and bird
detection, rain-rate determinations,
rain attenuations studies, and similar
studies. Results of these studies have
been reported in numerous publications
and at the Meteorology Radar
Conferences. More recently, the major
emphasis has been on providing support
for the NASA Storm Hazards Program
conducted by NASA Langley Research
Center and the COMSTAR Communications
Experiment run by the Applied Physics
Laboratory of the Johns Hopkins
University.
The Storm Hazards Program is a
major facility user during the thunder-
storm season. This program contains a
number of different, but interdependent,
experiments. The overall goal of the
program is to improve the knowledge of
severe convective storms and how they
affect aircraft design and operation.
An F106B aircraft storm penetration
experiment is the keystone of the entire
program. It involves flying the highly
instrumented jet aircraft into
thunderstorm cells to measure the
effects of turbulence, direct lightning
strikes, and heavy rain on the aircraft
structure and the avionics. On-board
instruments measure current, current
change, the time rate-of-change in
electric and maganetic fields, and total
charge, as well as 3-axis accelerations.
Other experiments measure the X-ray and
optical signature of the lightning, the
chemistry of convective thunderstorm
cells, and the water thickness on the
airplane skin during encounters with
heavy rain.
An AFGL turbulence experiment uses
the F106B aircraft accelerometer data to
correlate with the turbulence measured
in the radar volume by the SPANDAR
radar .
-A Langley airborne doppler radar
experiment uses the F106B data as an in
situ measure of turbulence. This data
is correlated with measurements - made
with a K-band doppler radar in the
Wallops Skyvan (NASA 430) airplane.
A Wallops/University of Oklahoma
experiment uses the UHF radar to
actively detect lightning channels in
order to provide high-range resolution
of lightning activity in a small region
of space.
An AFGL passive lightning detection
study uses a large '(60-foot) microwave
dish to detect the natural radiation
created by lightning activity. Closely
related is a cooperative experiment
conducted by Rome Air Force Base to
detect any radiation at 430 MHz gene-
rated by the airplane itself.
The Severe Storm Dynamics Investi-
gation is a 'Wallops program that seeks
to understand the nature of. severe
storms and the correlations among the
parameters characterizing such storms.
'The experiment utilizes the vast amount
of data that can be collected at ASRF to
study storm properties.
In studies not connected with storm
hazards, a COMSTAR communications
experiment uses the SPANDAR radar to
measure the amount of precipitation
along an earth-to-satellite communica-
tions path. This data is used to
develop rain fade statistics for high-
frequency communications satellites.
The National Severe Storms
Laboratory (NSSL) is conducting a wind
profiling experiment which uses both
radars in their most powerful and most
sensitive configuration. They are at-
tempting to measure the profile of the
horizontal component of the wind from
the ground up to the height of the
tropopause.
4.0 PROCEDURES FOR USE
Since it was established in 1945,
Wallops has maintained an open door
policy to both government and inde-
pendent investigators from the United
States and abroad. The wide array of
instrumentation facilities used on the
rocket range has been made available to
the scientific community to support many
types of scientific studies. This
policy applies to the ASRF as well.
Currently, there is no user's fee
attached to the use of the facility.
Only those costs above and beyond normal
operating costs are charged to the user.
ORIGINAL PAGE 19
OF POOR QUALITY
More information about use of the
facility can be obtained from either of
the authors or by writing to the
Director of Suborbital Projects and
Operations, NASA Goddard Space Flight
Center/Wallops Flight Facility, Wallops
Island, VA 23337.
REFERENCES
Baum, R. K., and T. J. Seymour, 1979:
In-Flight Evaluation of a Severe
Weather Avoidance System for
Aircraft. AFFOL-TM-79-45-EES, GPO.
Cox, Ronald, and Robert Masterson, 1969:
Facilities for Atmospheric
Research, Report No. 11, NCAR
Facilities Laboratory.
Krider, E. Philip, A. E. Pifer, and
M. A. Uman, 1980: An Automatic
Locating System for Cloud-to-Ground
Lightning. Lightning Technology,
Ed. Pitts, 205-214, NASA CP-2128.
LeVine, D. M., and E. P. Krider, 1977:
The Temporal Structure of HF and
VHF Radiation during Florida
Lightning Return Strokes, Geophys.
Res. Lett., 4, 13-16.
, 1978: RF Radiation from
"Lightning. NASA TM 78095.
, 1980: Sources of the Strongest
"RF Radiation from Lightning, 1980.
J. Geophys. Res. 85, 4091-4095.
Parsons, C. L., J. C. Gerlach, and"
M. E. Williams, 1982A: An Inter-
comparison of Ground-Based Total
Ozone Instruments. J. Appl.
Meteor., 21, 88-104.
, , and M. Whitehurst, 1982B:
A Fourier Transform Spectrometer
for Visible and Near-Ultraviolet
Measurements of Atmospheric
Absorption. NASA TM 73297.
Poehler, H. A., 1978: A Preliminary
Test of the Application of the
Lightning Detection and Ranging
System (LDAR) as a Thunderstorm
Warning and Location Device for
the FAA. NASA CR-154629.
, and C. L. Lennon, 1979:
Lightning Detection and Ranging
System (LDAR) Description and
Performance Objectives.
NASA TM 74105.


Facilities for meteorological research at NASA Goddard/Wallops Flight Facility

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