P-3 Orion - WFF

CAR is a multi-wavelength scanning radiometer for determining albedo of clouds in the visible and near-infrared and measuring the angular distribution of scattered radiation and bidirectional reflectance of various surface types. It acquires imagery of cloud and Earth surface features.

For details, visit: https://car.gsfc.nasa.gov/

The Broadband Radiometers (BBR) consist of modified Kipp & Zonen CM-22 pyranometers (to measure solar irradiance) and CG-4 pyrgeometers (to measure IR irradiance) (see http://www.kippzonen.com/). The modifications to make these instruments more suitable for aircraft use include new instrument housings and amplification of the signal at the sensor. The instruments are run in current-loop mode to minimize the effects of noise in long signal cables. The housing is sealed and evacuated to prevent condensation or freezing inside the instrument. Each BBR has the following properties: Field-of-view: Hemispheric Temperature Range: -65C to +80C Estimated Accuracy: 3-5% Data Rate: 1Hz

Fine depth resolution profiling of the top 100 m of the ice column is achieved with this radar designed to map variations in the snow accumulation rate. When operated from aircraft, it operates from 600 to 900 MHz providing 28-cm depth resolution in ice and when operated on the ground (500 MHz to 2 GHz) a 5.6-cm depth resolution in ice is achieved. This fine depth resolution enables area extensive spatial mapping of the annual accumulation layers.

The AXCTDs measure the ocean salinity, or saltiness (proportional to conductivity), and temperature, which are necessary 1) for computing ocean density, stability and buoyancy, and 2) for identifying different ocean water masses.

The Airborne Topographic Mapper (ATM) was a scanning LIDAR developed and used by NASA for observing the Earth's topography for several scientific applications, foremost of which is the measurement of changing arctic and antarctic icecaps and glaciers. It typically flies on aircraft at an altitude between 400 and 800 meters above ground level, and measures topography to an accuracy of ten to twenty centimeters by incorporating measurements from GPS (global positioning system) receivers and inertial navigation system (INS) attitude sensors.

The ATM instruments was based at NASA's Wallops Flight Facility (WFF) in Virginia. They commonly fly aboard the NASA P3-B based at WFF and have flown aboard other P-3 aircraft, the NASA DC-8, several twin-otters (DHC-6), and a C-130; they can fly on most Twin Otter/King Air-class aircraft. The ATM has flown surveys in Greenland nearly every year since 1993. Other uses have included measurement of sea ice, verification of satellite radar and laser altimeters, and measurement of sea-surface elevation and ocean wave characteristics. The altimeter often flies in conjunction with a variety of other instruments. The ATM has been participating in NASA's Operation IceBridge since 2009.

The ATM program was terminated in 2022.

The AMPR is a total power passive microwave radiometer producing calibrated brightness temperatures (TB) at 10.7, 19.35, 37.1, and 85.5 GHz. These frequencies are sensitive to the emission and scattering of precipitation-size ice, liquid water, and water vapor. The AMPR performs a 90º cross-track data scan perpendicular to the direction of aircraft motion. It processes a linear polarization feed with full vertical polarization at -45º and full horizontal polarization at +45º, with the polarization across the scan mixed as a function of sin2, giving an equal V-H mixture at 0º (aircraft nadir). A full calibration is made every fifth scan using hot and cold blackbodies. From a typical ER-2 flight altitude of ~20 km, surface footprint sizes range from 640 m (85.5 GHz) to 2.8 km (10.7 GHz). All four channels share a common measurement grid with collocated footprint centers, resulting in over-sampling of the low frequency channels with respect to 85.5 GHz.

The Airborne Multichannel Microwave Radiometer (AMMR) measures thermal microwave emission (in degrees Kelvin of brightness temperature) from surface and atmosphere. The up-looking radiometer at 21 and 37 GHz is a component of AMMR that was developed in the 1970's for precipitation measurements from an aircraft. The entire AMMR assembly covers a frequency range of 10-92 GHz. The 21/37 GHz unit has been flown in many types of aircraft during the past three decades in various field campaigns. It was refurbished during the year 2000 and is ready for flight again.

The fixed-beam Dicke radiometer has a beam width of about 6 degrees and is currently programmed with radiometric output every second. The temperature sensitivity is < 0.5 K, and the calibration accuracy is about ±4 K. The calibration is performed on the ground by viewing targets of known brightness (e.g., sky and absorber with known brightness temperature). The unit can be installed in one of the windows of the NASA P-3 aircraft so that it views at an angle of about 15º from zenith. Thus, it is necessary to spiral the aircraft gradually down to region below the freezing level in order to make measurements effectively. Ideally, the aircraft descends at the rate of about 1 km per 5 minutes. The system requires a bottle of N2 gas to keep the wave guides dry during the in-flight operation.

The Airborne Earth Science Microwave Imaging Radiometer (AESMIR) is a passive microwave airborne imager covering the 6-100 GHz bands that are essential for observing key Earth System elements such as precipitation, snow, soil moisture, ocean winds, sea ice, sea surface temperature, vegetation, etc.

AESMIR’s channels are configured to enable it to simulate various channels on multiple satellite radiometers, including AMSR-E, SSMI, SSMIS, AMSU, ATMS, TMI, GMI, ATMS, & MIS. Programmable scan modes include conical and cross-track scanning. As such, AESMIR can serve as an inter-satellite calibration tool for constellation missions (e.g., GPM) as well as for long-term multi-satellite data series (Climate Data Records).

The most unique/cutting edge feature of the instrument is its coverage of key water cycle microwave bands in a single mechanical package—making efficient & cost-effective use of limited space on research aircraft, and maximizing the possibilities for co-flying with other instruments to provide synergistic science. State-of-the-art calibration, fully-polarimetric (4-Stokes) observations, and the ability to accommodate large/heavy sensors (up to 300 kg) are other features of AESMIR. AESMIR currently flies on the NASA P-3 aircraft.

With these capabilities, AESMIR is an Earth Science facility for new microwave remote sensing discovery, pre-launch algorithm development, and post-launch Calibration/Validation activities, as well as serving as a technology risk reduction testbed for upcoming spaceborne radiometers. In the latter role, AESMIR is already supporting the GPM, Aquarius, and SMAP missions.

Aerosols (particulate matter) have a dramatic effect on radiative forcing of the climate, in some cases cooling and in other cases warming. The Fourth Assessment Report of the IPCC estimates that direct radiative forcing due to all aerosols is a cooling of -0.50 W m-2 with absorbing aerosol (black carbon) responsible for a warming of +0.22 W m-2, but the uncertainties associated with these numbers are very large. Better measurements of the optical properties of aerosols, especially absorption coefficient and asymmetry parameter, and their spatial and temporal distribution are required to reduce these uncertainties and improve the ability of models to predict climate change. Aero3X was designed to provide such measurements. It is a light weight (11 kg), compact (0.25 x 0.30 x 0.6 m), and fast (1 Hz sample rate) instrument intended for use on an Unmanned Aerial System (UAS) but suitable for flight on other aircraft and for surface measurements. Aero3X uses an off-axis cavity ring-down technique to measure extinction coefficient and a reciprocal nephelometry technique for measurement of total-, forward- and back-scatter coefficients at wavelengths of 405 nm and 675 nm. Its outstanding precision (0.1 Mm-1) and sensitivity (0.2 Mm- 1) allow the determination of absorption coefficient, single-scattering albedo, estimates of backscatter to extinction ratio and asymmetry parameter at both wavelengths, and Angstrom exponent. Together with its humidification system for measurement of the dependence of aerosol optical properties on relative humidity, these represent a complete set of the aerosol optical properties important to climate and air quality. Aero3X was designed to operate in pollution plumes where NO2 may cause interference with the measurement, therefore, a measurement of NO2 mixing ratio is also made.