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

 

 

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.