The CALMIT "SpecLab" provides a facility for collecting spectral data under controlled, experimental conditions. SpecLab provides research facilities, storage space for the field program, and office space. At the core of the facility is "dark room" where spectral measurements can be made in a systematic fashion. Several types of spectroradiometer systems can be mounted in a very convenient, yet controlled, manner using a versatile, ceiling-mounted "sensor platform." A variety of laboratory equipment is available to researchers and students including a Shimadzu UV-2501PC (UV-VIS) recording spectrophotometer and a LI-COR 3100 area meter.
Supplemental artificial light for culturing algae and plants is provided by numerous 400W metal-halide lights, while spectral measurements are made using 500W halogen lights. SpecLab also contains facilities and equipment for analyzing water samples as well as large ovens for drying vegetation samples.
Field Research Facility
The CALMIT Field Research Facility (CFRF) is located at the University of Nebraska Agricultural Research and Development Center-Ithaca (ARDC), which is about 35 miles north and slightly east of Lincoln, near Mead, Nebraska
The ARDC is a 9,000-acre experiment station, operated under the aegis of the Agricultural Research Division of the Institute of Agriculture and Natural Resources.
Annually, CALMIT staff participate in a Field Day at the Field Research Facility. The field remote-sensing program is one of the major program areas under the aegis of CALMIT. An impressive array of facilities and equipment combine to provide faculty, staff, students, and visiting scientists with an unusual opportunity to conduct field-oriented investigations. The emphasis of the field activities is on close-range remote sensing, but data collected by means of many other related technologies can be linked to the spectral data.
Aerial Remote Sensing Platform
CALMIT staff members, in cooperation with the UNL Department of Electrical Engineering and the UNO Aviation Institute, developed (2001) an aerial remote sensing platform for collection of spectral data. The platform is a Piper Saratoga, which has undergone extensive modifications to facilitate deployment of sensors. In 2005, the AISA-Eagle (AE) Hyperspectral Imager (VNIR) replaced the AISA-Classic (2002) as the primary on-board sensor. The AE, programmable to 512 spectral channels, acquires data for researchers at a spatial resolution of 1 and 2 meters.
All-Terrain Terrestrial Vehicle Data Collection Platform
CALMIT staff have constructed a unique, versatile all-terrain instrument platform, which is being used primarily for collecting spectral data in agricultural/cropland environments. The system, referred to as "Goliath," has great potential for "precision-agriculture" applications. "Goliath" provides a high-clearance mechanism for making measurements such as spectral reflectance in field settings. The pertinent characteristics of the Goliath platform include a ground clearance of 72 inches, a width of 102 inches, and wheels positioned for movement through crops with 30-inch rows. The tracked wheels allow access to difficult landscape positions.
The working platform on Goliath is 8 x 9 feet. The Goliath platform itself has a driver's seat and four scientist desks. Thus, up to five passengers/scientists can be accommodated during data-collection missions. The ample desk space allows instrument operations to be executed easily and efficiently. The hydraulic boom is 15 feet 6 inches long when stowed, but can be extended to 28 feet during data collection. It can be raised to a height of approximately 40 feet above the ground surface, and rotated through a full circle around the platform (note that a jib can be added to increase the sensor elevation to approximately 50 feet.).
The boom can be lowered nearly to ground level to accommodate either sensor attachment or calibration by means of a reference panel on, for example, a tripod. The maximum sensor payload for the boom, at full extension, is ~100 pounds. The operator has complete control of the sensor position from the deck. That is, the operator not only has control of the boom, and thus sensor field-of-view, but also the nadir or off-nadir position of the sensor. That view angle can be changed and verified easily and quickly. The Goliath system can be towed long distances by means of a specially constructed trailer.
CALMIT operates a 24-foot pontoon boat, which has been specially modified for collection of spectral data above, at, and beneath the surface. The boat provides an excellent workspace for data collection on lakes and reservoirs.
In addition to equipment for monitoring radiation fluxes, the boat carries a GPs receiver, onboard computing, and portable water-quality and analysis equipment. Researchers often operate our numerous pyranometer, terrestrial-quantum, and underwater-quantum sensors when collecting spectroradiometer data in the field.
In the case of the underwater sensors, upwelling and downwelling PAR are typically measured at two different depths, as a means of calculating the rate of extinction of light in lakes and reservoirs. The boat can be safely towed over long distances to facilitate study of distant aquatic systems. Water samples are typically collected and analyzed in support of our remote-sensing research on lakes and reservoirs. Detailed analyses of plant pigments, specific cations and anions, and other parameters are available through our own facilities, those of our research partners, and other university collaborators. CALMIT owns portable analysis equipment including instrumentation for measuring conductivity, turbidity, alkalinity, and other physicochemical parameters. A portable laboratory, with a spectrometer and reagent chemicals, provides additional measurement capabilities. With the portable and lab-based instrumentation, we are able to make measurements on-site, on a same-day basis, at remote locations and/or in a clinical-laboratory setting. This affords repeatable water sampling linked directly to remotely sensed data either from our spectroradiometers or in conjunction with aircraft/satellite overpasses.
Van and Radar Scatterometer
Radar remote sensing is increasingly important at CALMIT. Working with the departments of Agricultural Meteorology and Electrical Engineering, studies are being done on L-and C-band radar backscatter from wetland vegetation. A major tool in these studies is a radar-equipped van, which has a hydraulic boom that can be extended out over a study area and can measure radar backscatter at multiple frequencies, polarizations, angles and heights.
An important feature of the van is that it can match the characteristics of three satellite-borne imaging radars including the Japanese Space Agency JERS-1, the European Space Agency ERS-1 and the ERS-2. Additionally the van can emulate many properties of the Canadian RADARSAT and Russian ALMAZ satellites.
Several types of field spectroradiometers are used by CALMIT researchers in data collection. From the early 1980's to the mid-1990's, the "workhorse" was a Spectron SE-590, which collects 252 discrete channels of information from 368 to 1114 nm. A second SE-590 was purchased in 1994 to facilitate collection of incoming solar irradiance concurrent with target scanning, to provide instantaneous profiles of reflectivity for selected targets. Such an approach allowed for data collection on days when the irradiance conditions were changing rapidly. The SE-590's are now primarily used for indoor-experimental testing and calibration.
In 1995, our first Ocean Optics PSD1000-C spectrometer was purchased. This instrument collected 1100 discrete channels of information from 300 to 900 nm, using two fiber-optic cables. The two cables are configured in a manner analogous to the SE-590 systems, so that simultaneous incoming and reflected solar irradiance are measured. In 2001, four Ocean Optics USD-2000 systems were acquired, and since that time, much of our day-to-day data collection is done with these spectroradiometers mounted on Goliath, boat platforms, and even underwater. Having two dual-fiber systems allows for simultaneous data collection by two field crews.
The first Analytical Spectral Device (ASD) FieldSpec FR system, purchased in early 1998, provides hyperspectral coverage from 350 to 2500 nm. The additional capability in the mid-infrared spectrum is important with regard to staff research involving agricultural vegetation. The system was configured to allow positioning both on the boom of the Goliath vehicle and by one individual carrying it on foot into the field. The ASD can be used for assessing vegetation at both canopy and leaf levels (with optional leaf clip). By 1999, a second ASD-FR was acquired, and that system is now part of our standard aircraft-sensor deployment. The latter is bore-sighted with a digital-video camera.
In 2001, CALMIT purchased a UniSpec radiometer capable of collecting data in 256 channels ranging from 300 to 1100 nm. The UniSpec provides us with capability for not only assessing water quality but also vegetation at leaf-level.