HALO#
The German High Altitude and Long-Range Research Aircraft (HALO) is a modified Gulfstream G550 and operated by the German Aerospace Center (DLR) is equipped with remote sensing instruments and a facility to launch dropsondes. It has long endurance (upto 9 flight hours), a long range (about 8000 km), and a high ceiling (15.5 km). Its flight speed is typically 240 m/s at 14 km, and 220 m/s at 9 km. As the aircraft is build to be flying at high altitudes, most of the instrumentation observes the atmosphere (and in particular clouds) from the nadir perspective.
Instrumentation#
The instrumentation of the HALO aircraft is based on contributions from various universities and research institutions. Each instrument is developed and operated by an individual group, which leads to a modern instrumentation suite and well trained operators. This section includes individual contact points for the specific instruments.
In particular, the instrumentation consists of broadband radiometers (BACARDI), basic instrumentation (BAHAMAS), a dropsonde launching system (Dropsondes), the active (radar) and passive microwave package (HAMP), irradiance spectrometers (SMART), a thermal imager (VELOX), an infrared radiometer (VELOX-KT19), a water vapor differential absorption lidar (WALES) and spectral and polarization resolving imagers (specMACS).
BACARDI
A set of broadband radiometer measuring upward and downward irradiance in the solar (0.2 - 3.6 micrometer) and terrestrial (4.5 - 42 micrometer) spectral range.
PI: André Ehrlich (LIM)
BAHAMAS
The Basic HALO measurement and sensor system (BAHAMAS) includes aircraft state variables, position, three-dimensional turbulent winds (from five hole probe on boom), humidity (diode laser), temperature and pressure.
PI: DLR-FX
Dropsondes
AVAPS dropsonde system using Vaisala RD-94 sondes to measure temperature with an accuracy of 0.2 ºC, humidity with an accuracy of 2 %RH, pressure with an accuracy of 0.4 hPa. Winds are derived from GPS position measurements with an estimated accuracy of 0.1 m/s. The receiver can track 8 sondes simultaneously.
PI: Bjorn Stevens(MPI-M)
HAMP
Radar: The radar is a nadir staring instrument that measures in the water-vapor window at a frequency of 35.5 GHz (Ka-band). This system, similar to cloud radars operated on the Barbados Cloud Observatory, is operated with a 200 ns pulse length and a pulse repetition frequency of 5kHz. Two receivers provide co- and cross-polarization reflectivity measurements. Radiometer: Three downward looking radiometer modules passively measure the microwave emissions of Earth’s atmosphere in twenty-six channels probing two water vapor and two oxygen absorption features, as well as window channels. Beam widths of 2.7º to 5.0º and a sampling rate of about 1s.
PIs: Felix Ament(UHH) | Bjorn Stevens(MPI-M) | Lutz Hirsch(MPI-M) | Florian Ewald(DLR)
SMART
The Spectral Modular Airborne Radiation measurement sysTem (SMART) measures spectral irradiances from zenith and nadir oriented sensors. An additional nadir looking sensor measures radiances. Measurements span the visible and near infrared (300 nm to 2200 nm) with a 2 nm to 3 nm spectral resolution for wavelengths shorter than 1000 nm and a 10 nm to 15 nm spectral resolution for longer wavelengths.
PI: Manfred Wendisch(LIM)
specMACS
The spectrometer of the Munich Aerosol Cloud Scanner (specMACS) consists of two camera systems, both looking nadir, one in the visible/near-infrared (400 nm to 1000 nm), and another in the short-wave infrared (1000 nm to 2500 nm). The systems produce a spectrally resolved line image with 1312 pixels covering a 32.7º field of view in the visible/near infrared, and with 320 pixels covering a 35.5º field of view in the short-wave infrared.
PI: Bernhard Mayer(LMU)
VELOX
VELOX is a thermal infrared spectral imager (VELOX327k veL, 640 pixel by 512 pixels) with a synchronized filter wheel (at 100 Hz) covering six spectral channels in the thermal infrared wavelength range from 7.7 to 12.0 micrometer. The instrument measures the brightness temperature of upward radiance in a field-of-view of 35.49° by 28.71°.
PI: Manfred Wendisch(LIM)
VELOX KT-19
Thermal infrared radiometer measuring the brightness temperature of nadir radiance between 9.6 and 11.5 micrometer. The field-of-view of 2.3° is located in the center of the VELOX images.
PI: Manfred Wendisch(LIM)
WALES
WALES operates at four wave-lengths near 935 nm to measure water-vapor mixing ratio profiles covering the whole atmospherebelow the aircraft. At typical flight speeds it has a resolution of 200 m in the vertical and 6 km in the horizontal. The system also contains additional aerosol channels at 532 nm and 1064 nm with depolarization. WALES uses a high-spectral resolution technique, which distinguishes molecular from particle backscatter, to make direct extinction measurements with a resolution of 15 m in the vertical and 200 m in the horizontal.
PI: Martin Wirth(DLR)