Twin Otter - GRC

The Center has been developing a wideband radar altimeter that operates over the frequency range from 13 to 17 GHz. The primary purpose of this radar is high precision surface elevation measurements over polar ice sheets. The data collected with this radar can be analyzed in conjunction with laser-altimeter data to determine thickness of snow over sea ice. The radar has been flown on a NASA DC-8 aircraft, and the NSF provided a Twin Otter aircraft.

TSI Integrating Nephelometers are designed specifically for studies of direct radiative forcing of the Earth’s climate by aerosol particles, or studies of ground-based or airborne atmospheric visual air quality in clean areas. They may also be used as an analytical detector for aerosol particles whenever the parameter of interest is the light-scattering coefficient of the particles after a pretreatment step, such as heating, humidification, or segregation by size. The light-scattering coefficient is a highly variable aerosol property. Integrating Nephelometers measure the angular integral of light scattering that yields the quantity called the aerosol scattering coefficient, which is used in the Beer-Lambert Law to calculate total light extinction.

The Ames' Extinction Scattering Optical Property (AESOP) instrument measures aerosol extinction coefficient using cavity ring-down technology and scattering coefficient using reciprocal nephelometry. Measurements are made at two wavelengths (675 nm and 405 nm) with sufficient accuracy to obtain aerosol absorption coefficient, single scattering albedo, and the three Ångström exponents.

WISE is an airborne sounder designed to measure the nadir ice thickness of warmer and fractured glacier. Its design is based on a successful planetary sounder MARSIS that enables scientist to discover layered water-ice deposits near Mars poles.

The airborne sounder uses 15-300 meter long wavelengths in order to penetrate into rough surfaces, voids, and cracks before they are reflected by the interface between ice and bedrock. This makes the system well suited for the study of outlet glaciers whose internal structures are very complicated due to fast-moving surfaces and proximity to a relatively warm body of ocean.

Such an investigation will provide us with valuable information such as ice stratigraphy and the ground slope of the bedrock layer as well as ice thickness, which is very important to construct a reliable ice-flow model.

SIMPL is an advanced-technology airborne laser altimeter developed through NASA’s ESTO Instrument Incubator Program. Simultaneously measures surface topography, roughness and slope as well as scattering properties to differentiate surface types. SIMPL is a technology and remote sensing pathfinder for next-generation, high-efficiency, spaceflight laser altimeters. Developed with a focus on ice sheet elevation and its change, sea ice thickness and its change, and icy moon surface processes.

PolSCAT is a Ku-band polarmetric scanning scatterometer operating at 13.95 GHz. with an approved NASA license. The transmitting polarizations of PolSCAT, alternating between Vertical and Horizontal, from pulse to pulse. Two receivers detect the V and H polarized radar echoes simultaneously allowing for measurements of VV, HH, VH, and HV radar responses. It provides scalable resolution, between 3,000 and 20,000 feet AGL.

The PolSCAT antenna assembly includes two axis gimbals for conically scanning, parabolic antenna, which is controlled from 0° (nadir) to 65 degrees. It was designed and built to investigate the benefits of active microwave for the remote sensing of high resolution snow-water-equivalent (SWE).

PolSCAT’s flexible design is compatible with many aircraft. It has flown on the NCAR C-130, NASA’s DC-8, P-3, and Twin Otter International’s, Twin Otter. Flown more than 500 hours in support of NASA’s Cold Land Process (CLPX) campaigns, PolSCAT is a very mature instrument.

PALS is a combined polarimetric radiometer and NASA licensed radar sharing a rotating planar array antenna. The PALS instrument includes a combined L-band radiometer and scatterometer , operating at 1.413 GHz and 1.26 GHz respectively. It was designed and built to investigate the benefits of combining passive and active microwave sensors for Ocean salinity and Soil moisture remote sensing. It is the prototype for the Aquarius and SMAP missions and its flexible design is compatible with many aircraft.

The PALS radar and radiometer time share a dual pole, dual frequency planner array antenna. The antenna configuration can be fixed or rotating. It provides scalable resolution, between 3,000 and 20,000 feet AGL. It is an Aquarius and SMAP test bed.

PALS has flown on the NCAR C-130, NASA’s P-3 and Twin Otter International’s, Twin Otter. It is a very mature instrument, and has flown more than 800 hours, in support of NASA campaigns.

The Center for Remote Sensing of Ice Sheets (CReSIS) has developed radars (MCoRDS) that operate over the frequency range from 140 to 230 MHz with multiple receivers developed for airborne sounding and imaging of ice sheets. MCoRDS radars have an adjustable radar bandwidth of 20 MHz to 60 MHz. Multiple receivers permit digital beamsteering for suppressing cross-track surface clutter that can mask weak ice-bed echoes and strip-map synthetic aperture radar (SAR) images of the ice-bed interface. With 200 W of peak transmit power, a loop sensitivity > 190 dB is achieved. These radars are flown on twin engine and long-range aircraft including NASA P-3 and DC-8.