The NASA Langley High Altitude Lidar Observatory (HALO) is used to characterize distributions of greenhouse gasses, and clouds and small particles in the atmosphere, called aerosols. From an airborne platform, the HALO instrument provides nadir-viewing profiles of water vapor, methane columns, and profiles of aerosol and cloud optical properties, which are used to study aerosol impacts on radiation, clouds, air quality, and methane emissions. When the water vapor, aerosol and cloud products are combined it provides one of the most comprehensive data sets available to study aerosol cloud interactions. HALO is also configured to provide in the future measurements of the near-surface ocean, including depth-resolved subsurface backscatter and attenuation.
The APR-3 is a three frequency (13, 35, and 94 GHz), Doppler, dual-polarization radar system. It has a downward looking antenna that performs cross track scans, covering a swath that is +/- 25 to each side of the aircraft path. Additional features include: simultaneous dual-frequency, matched beam operation, simultaneous measurement of both like- and cross-polarized signals at both frequencies, Doppler operation, and real-time pulse compression (calibrated reflectivity data can be produced for large areas in the field during flight, if necessary).
The Advanced Vertical Atmospheric Profiling System (AVAPS) is the dropsonde system for the Global Hawk. The Global Hawk dropsonde is a miniaturized version of standard RD-93 dropsondes based largely on recent MIST driftsondes deployed from balloons. The dropsonde provides vertical profiles of pressure, temperature, humidity, and winds. Data from these sondes are transmitted in near real-time via Iridium or Ku-band satellite to the ground-station, where additional processing will be performed for transmission of the data via the Global Telecommunications System (GTS) for research and operational use. The dispenser is located in zone 61 in the Global Hawk tail and is capable of releasing up to 88 sondes in a single flight.
The NASA Langley Research Center DAWN (Doppler Aerosol WiNd) lidar system employs a pulsed, solid-state laser operating at 2053 nm wavelength. It pulses at 10 Hz with up to 100 mJ/pulse which are 180 ns long. Using a wedge scanner, several different azimuth angles can be measured below the aircraft, all at a 30 degree off-nadir angle. Multiple azimuth angles enable horizontal wind calculation, mitigate cloud obscurations, and measure atmospheric variability. DAWN can provide vertical profiles of the zonal (u) and meridional (v) components of the horizontal wind below the aircraft, typically at ~60 meter resolution. Various vertical and horizontal resolutions are possible in post processing. DAWN can also provide vertical profiles of line of sight (LOS) wind speed at each azimuth angle. It can also be operated to stare persistently at any particular azimuth angle to simulate what a satellite such as European Space Agency Atmospheric Dynamics Mission (ADM) Aeolus would observe. DAWN signal returns also permit retrieval of vertical profiles of relative aerosol backscatter, planetary boundary layer height, and wind turbulence.
High Altitude Monolithic Microwave integrated Circuit (MMIC) Sounding Radiometer
The High Altitude Monolithic Microwave integrated Circuit (MMIC) Sounding Radiometer (HAMSR) is a microwave atmospheric sounder developed by JPL under the NASA Instrument Incubator Program. Operating with 25 spectral channels in 3 bands (50-60 Ghz, 118 Ghz, 183 Ghz), it provides measurements that can be used to infer the 3-D distribution of temperature, water vapor, and cloud liquid water in the atmosphere, even in the presence of clouds. The new UAV-HAMSR with 183GHz LNA receiver reduces noise to less than a 0.1K level improving observations of small-scale water vapor. HAMSR is mounted in payload zone 3 near the nose of the Global Hawk.
HAMSR was designed and built at the Jet Propulsion Laboratory under the NASA Instrument Incubator Program and uses advanced technology to achieve excellent performance in a small package. It was first deployed in the field in the 2001 Fourth Convection and Moisture Experiment (CAMEX-4) - a hurricane field campaign organized jointly by NASA and the Hurricane Research Division (HRD) of NOAA in Florida. HAMSR also participated in the Tropical Cloud Systems and Processes (TCSP) hurricane field campaign in Costa Rica in 2005. In both campaigns HAMSR flew as a payload on the NASA high-altitude ER-2 aircraft. It was also one of the payloads in the 2006 NASA African Monsoon Multidisciplinary Activities (NAMMA) field campaign in Cape Verde - this time using the NASA DC-8. HAMSR provides observations similar to those obtained with microwave sounders currently operating on NASA, NOAA and ESA spacecraft, and this offers an opportunity for valuable comparative analyses.
