TRACE-P Project Measurements
The Langley Research
Center GTE Project Office is responsible for making a number
of measurements during the mission which will be needed
by the Principle Investigators in the analysis of their measurements. These measurements (Table 1) include many
parameters typically referred to
as ancillary and housekeeping measurements. All
measurements are recorded at 1 hz. by the Project Data System and are immediately available
to the PIs. The PIs may
record these measurements in real time as a result of their being
routed to the PI racks via an RS-232 line from the Serial Distribution
System. These measurements are also available in real time at the PIs’ rack
via TV monitors which are part of the Video Distribution System. Immediately after each flight these measurements
are available to PIs via a computer diskette which includes data
at 10-second intervals. Also,
a hard paper copy with data at 1-minute intervals will be immediately
available.
Following Table 1
are a number of notes and brief instrument descriptions giving
further information about the instrument or the measurement. Table
2 presents measurement ranges and accuracies, mostly for
P-3B instruments. Other DC-8 measurement ranges and accuracies
are available in the DC-8 Handbook reference. Table
3 (requires
Adobe Reader-download here) presents equations used in the
calculation of most of the calculated parameters noted in Table
1. It is intended that
the above material provide only enough detail to enable the user
to decide the applicability of that parameter to analysis needs. Details
of converting from counts or volts to engineering quantities
are documented elsewhere. Any other required detail is available from
the Langley GTE Project Office.
Table 1. TRACE-P Project
Measurements
Parameter
|
Units
|
DC-8 Origin
|
P-3B Origin
|
Julian
Day
|
day
|
GPS
Receiver
|
GPS
Receiver
|
Time
|
HM.S
|
GPS
Receiver
|
GPS
Receiver
|
Time
|
HM.S
|
-
|
FMS +
|
Latitude
|
degs
|
INS +
|
FMS
|
Longitude
|
degs
|
INS
|
FMS
|
Pitch
|
degs
|
INS
|
Project
clinometer
|
Roll
|
degs
|
INS
|
Project
clinometer
|
Wind
speed
|
knots
|
INS
|
FMS
|
Wind
direction
|
degs
|
INS
|
FMS
|
True
air speed
|
knots
|
CADC
Eq. 2 *
|
FMS
|
True
air speed
|
knots
|
-
|
Project
Sensor Eq. 2 *
|
Ground
speed
|
knots
|
INS
|
FMS
|
True
heading
|
degs
|
INS
|
FMS
|
Drift
angle
|
degs
|
INS
|
-
|
Pressure
Altitude 1
|
feet
|
CADC
|
FMS
|
Pressure
Altitude
|
feet
|
-
|
Project Sensor
|
Radar
altitude
|
feet
|
Radar
Altimeter +
|
-
|
Indicated
air speed
|
knots
|
CADC
|
-
|
Vertical
speed
|
fpm
|
CADC
|
Project
Sensor
|
Distance
to go
|
nm
|
INS
|
-
|
Time
to go
|
min
|
INS
|
-
|
Alignment
status
|
-
|
INS
|
-
|
Align/from/to
|
-
|
INS
|
-
|
Mach
Number
|
-
|
CADC
Eq.1 *
|
Project
Sensor Eq. 1 *
|
Cross
track distance
|
nm
|
INS
|
-
|
Desired
Track
|
degs
|
INS
|
-
|
Track
angle error
|
degs
|
INS
|
-
|
Track
angle
|
degs
|
INS
|
FMS
|
D/F
point temp. 2
|
degs C
|
GE
1011 sensor +
|
GE
1011 sensor
|
D/F
point temp. 2
|
degs
C
|
EG & G
300 sensor + 3
|
-
|
D/F
point temp. 2
|
degs
C
|
Buck
Res. CR-1 sensor +
|
-
|
Static
air temp.
|
degs
C
|
Eq.
3 *
|
Project
Sensors Eq.
3 *
|
Total
air temp.
|
degs
C
|
A/C
sensor +
|
Project
sensor
|
Static
air temp.
|
degs
C
|
CADC
Eq. 3 *
|
FMS
|
Potential
temp.
|
degs
K
|
Eq.
4 *
|
Eq.
4 *
|
Cabin
Pressure 4
|
psi
|
A/C
sensor +
|
Project
Sensor
|
Cabin
altitude
|
feet
|
*
|
*
|
Total Pressure
|
mb
|
-
|
Project
sensor
|
Static
Pressure 5
|
mb
|
A/C
sensor
|
Project sensor
|
Differential
Pressure 6
|
mb
|
-
|
Project
sensor
|
Specific
humidity
|
g/kg
|
Eq.
6 *
|
Eq.
6 *
|
Partial
pressure H2O wrt H2O
|
mb
|
Eq.
5 *
|
Eq.
5 *
|
Partial
Pressure of H2O wrt Ice
|
mb
|
-
|
Eq.
5 *
|
Rel.
humid. wrt ice
|
%
|
Eq.
7 *
|
Eq.
7 *
|
Rel.
humid. wrt H2O
|
%
|
Eq.
7 *
|
Eq.
7 *
|
Sat.
vapor press. of H2O
|
mb
|
Eq.
5 & 3 *
|
Eq.
5 & 3 *
|
Sat.
vapor press. of H2O wrt ice
|
mb
|
Eq.
5 & 3 *
|
Eq.
5 & 3 *
|
IR
surface temp.
|
degs
C
|
Barnes
radiometer +
|
Heimann
Pyrometer +
|
Sun
elev. grd. ref.
|
degs
|
* 8
|
-
|
Sun
azim. grd. ref.
|
degs
|
* 9
|
-
|
Sun
elev. A/C ref.
|
degs
|
* 10
|
-
|
Sun
azim. A/C ref.
|
degs
|
* 11
|
-
|
Zenith,
fwd. nadir cloud
video
|
-
|
A/C
cameras
|
Project
cameras +
|
Storm
scope
|
-
|
+
|
+
|
weather
radar
|
-
|
+
|
-
|
Polar
Sat. images
|
-
|
A/C
system +
|
-
|
J(NO2)
zenith & nadir
|
-
|
Project
sensors +
|
-
|
Eppley
zenith & nadir
|
w/m2
|
-
|
Project
sensors +
|
Temperature
of Eppley Sensors
|
degs C
|
-
|
Project
Sensors
|
Notes:
* indicates a calculated parameter
+ indicates that
a description is included on the following pages
1. Pressure altitude is based
on the 1962 Standard Atmosphere.
2. Source of Td in equations.
3. Measurements on the DC-8 are acquired at rates of one to twenty
samples per second. Where
the rate is in excess of one sample per second the data are averaged
over a one-second period.
4. Based on 1962 Standard Atmosphere.
5. Pressure measured on external aircraft surface tangential to air
flow.
6. Pressure difference between total and static pressure; qc in equations
7. Calculated using ground reference frame and assuming platform is
a point in space. Calculation
accounts for Sun ray refraction through atmosphere. Solar
zenith is 90 degrees.
8. Calculated using ground reference frame and assuming platform is
a point in space. No
consideration of refraction. North
is 0 degrees; East is 90 degrees; and West is 270 degrees.
9. Calculated using aircraft reference frame which moves in roll,
pitch and yaw. Refraction
is considered.
10. Calculated
using aircraft reference frame which moves in roll, pitch and
yaw and measured relative to the aircraft nose. Directions
are: along right wing-
90 degrees; from rear-
180 degrees and along left wing- 270 degrees.
++ INSTRUMENTATION DESCRIPTIONS
++
J(NO2) Radiometer
(DC-8 & P-3B):
The J(NO2) radiometer
measures the radiative flux in the 300 to 380 nm wavelength region
using optical filters and a vacuum phototube detector. A dome-shaped
quartz diffuser is utilized to minimize the dependence of the
instrument response to the angle of incident light. Because the
radiometer measures the radiative flux and not the photolysis
rate of NO2, the instrument
is calibrated with a chemical actinometric system.
Dew/Frost Point
Temperature Hygrometer
General Eastern Model
1011B Aircraft Hygrometer (DC -8 & P-3B):
The 1011B system
consists of a sensing unit, a control/indicator unit, a power
unit, and cabling. The hygrometer is designed for aircraft applications
and operates on the chilled-mirror principle. A mirror is thermoelectrically
cooled until it reaches the dew/frost point temperature. The
presence of dew/frost on the mirror is sensed optically (via
a light emitting diode and photodetector) and the temperature
maintained by a feedback control circuit. The 1011B utilizes
a two-stage thermoelectric heat pump, temperature-stable linear
phototransistor detector, and a control circuit configured
for variable thickness settings.
EG&G Model 300
Microprocessor Controlled Humidity Analyzer (DC-8):
The model 300 humidity
analyzer is designed to measure moisture in gases for a wide
variety of laboratory and industrial applications. The hygrometer
utilizes the chilled mirror principle to determine water vapor
concentrations. The sampling system has been modified for airborne
applications and the mirror assembly is cooled via a three-stage
thermoelectric heat pump. The presence of dew or frost on the
mirror is sensed optically and maintained at optimal conditions
via a servo loop controlled by microprocessors and digital techniques.
The model 300 hygrometer utilizes a secondary or dry mirror for
reference or calibration channel to automatically compensate
the primary mirror system for changes in reflectivity to minimize
balancing cycles.
Buck Research Model
CR-1 Hygrometer(DC-8):
The CR-1 operates
on the chilled-mirror principle. A dew/frost layer is optically
sensed and mirror temperature controlled with feedback control
circuit similar to the 1011B system. In this instrument, however,
the mirror is cooled by LN2 boil-off through the mirror stem
and heated via a heating element wound around the upper portion
of the mirror stem.
Buck Research Model CR-2 Hygrometer (P-3B):
The model CR-2 instrument is a chilled mirror,
condensation type hygrometer. It
utilizes a closed-cycle cryocooler to cryogenically cool a mirror
surface and maintain it at the dew/frost point by means of a
heater/control system. Optical detectors are used for sensing condensate
on the mirror, and a thermistor imbedded in the mirror is used
to determine mirror temperature (dew/frost point). The instrument consists of a sensor assembly, crycooler, cryocooler
drive circuitry, and control /readout circuitry. A separate module displays operational and
output voltages, and allows manual control of the system, but
is not required.
Surface Temperature
Heimann Infrared
Radiation Pyrometer Model KT 19.85 (P-3B & DC-8):
The Heimann pyrometer
measures surface temperature in a non-contact mode. The instrument determines thermal energy remotely by sensing
infrared radiation in the 9.6 to 11.5 micron wave-length region
through focusing optics and a pyroelectric detector. A chopped
radiation method is used to modulate the infrared radiation intercepted
by the infrared detector. This is accomplished by an optical
chopper, basically mechanical blades driven by an electric motor,
which periodically interrupts the incident radiation from the
measured target to the detector. The detector is exposed to a
reference source at a known temperature during each interruption.
The Model KT 19.85 optics and detector are designed to maximize
performance for aircraft applications. The instrument optics
are customized for infinity focus with a 2 field of view.
Cloud Video (DC-8 & P-3B):
Cloud video is recorded
onboard the P-3B aircraft in zenith, nadir, and forward-looking
views. Panasonic Model GP-KS162 !/2-inch format color camera
images are recorded on S-VHS video cassette recorders. A wide
angle lens (130 FOV) is utilized on the zenith- and nadir-viewing
cameras and a zoom lens (45 to 90 FOV) on the forward-viewing
camera. The cameras have 480 lines of horizontal resolution and
are equipped with an electronic auto light control. The video
recorders have more than 400 lines of horizontal resolution and
selectable recording modes (SP and SLP) which determines recording
time and video quality. In-house camera and video recording equipment available at Ames
Research Center that best emulates the above described video system
will be employed on the DC-8 aircraft and will be described here
when they are defined.
Stormscope (DC-8 & P-3B):
BF Goodrich StormscopeTM
Series II Model WX-1000:
The StormscopeTM
is a passive thunderstorm mapping system designed for airborne
applications. The system consists of an antenna, processor, display,
and VHS video cassette recorder. The system maps electrical discharge
activity 360 around the aircraft. Features include four selectable
ranges up to a 200 nautical mile maximum and a switchable display
format with either a 360 circular view or 120 forward sector
view.
Total Air Temperature
System (DC_8):
The Rosemont 102
AH2Ag Total Air Temperature(TAT) system features an accurate,
quick response probe that measures the total temperature of air
outside the aircraft, using a platinum-resistance sensing element. This
value is warmer than Static Air Temperature(SAT) by reason of
aircraft speed. The TAT
is used by the CADC to compute the true airspeed.
Radar Altimeter
(DC-8):
A Honeywell APN-222
electronic altimeter system determines the aircraft’s altitude
above land or water(0 to 70000 ft on the DC-8) by means of reflected,
submicrosecond 4.3Ghz rf pulses. The
specified digital accuracy is ±0.5
% at all altitudes.
Inertial Navigation
System:
DC-8
The Delco Carousel
IVA-3 Inertial Navigation System(INS) operates by sensing aircraft
accelerations from a gyro-stabilized, four-gimbal, all-attitude
platform. Dual two-degree-of-freedom gyros, that feature self-generating
gas bearings, have very low drift characteristics and an excellent
turn-on repeatability. A
general purpose, microelectronic digital computer is part of
the system. Data are acquired from the system at two-second intervals.
The system accepts a true airspeed signal that is used to compute
wind speed and direction. INS measurements are routed to the CADC for calculations.
P-3B
The P-3B uses the
Honeywell YG1854 LASEREF SM IRS. The
inertial reference unit contains the ring laser gyros, accelerometers,
sensor electronics, computer electronics, interface electronics
and electrical interfaces with the aircraft necessary to perform
as a high-accuracy reference system. It
provides all attitude and heading data in true and magnetic North
reference, velocities and present position. IRS
measurements are routed to the FMS for calculations.
Weather Radar
System (DC-8):
A Collins WXR-700C
horizontal scanning, two-axis, gyrostabilized C-band radar antenna
is located in the nose of the DC-8 aircraft. Color
images are displayed on a Multi-Function Display (MFD) that is
also used to display the aircraft’s flight instrument system. The
Aircraft Manager can observe and record on video tape the same
weather display the flight crew is observing.
Cabin Altimeter
(DC-8):
The equivalent altitude
pressure in the cabin(0 to 10000 ft) is detected by a Rosemont
Mod 1241 A5CD cabin altimeter. The
signal output is sent to DADS for recording and display on the
CCTV.
Polar Satellite
Images (DC-8):
Weather pictures
from orbiting satellites are available on the DC-8 aircraft. A
Lockheed Automatic Picture Transmission (APT) System uses the
polar orbiting satellites NOAA 9, 10, 11 and 12. These
pictures can be used before a flight to assist in the planning
of flight tracks. When
on a remote deployment or during a flight, the onboard APT system
can be used to obtain near real-time observation of weather systems.