Space Station Agricultural Camera Observes Flooding in North Dakota
Ask a geologist or ecologist about remote sensing of the Earth—collecting information about a material or process without physically touching or sampling it—and they will likely mention Landsat; Advanced Spaceborne Thermal Emission and Reflection Radiometer, known as ASTER; Moderate Resolution Imaging Spectroradiometer, or MODIS; or other sensor systems that routinely collect data from orbit for the land surface, oceans, or atmosphere. Since the early 1970s, terrestrial global remote sensing has been the territory of the polar-orbiting, sun-synchronous satellite, but that is now changing with the addition of new remote sensing systems to the International Space Station.
One of the first new systems is the International Space Station Agricultural Camera, or ISSAC. The ISSAC was developed by students and faculty at the University of North Dakota, and its prime purpose is to collect data in support of agricultural activities and related research in the upper midwest of the United States. Today’s farmers use data and information from a variety of remote sensing satellites to understand weather systems and climate patterns and to monitor the health of their crops. The ISSAC will be another source of information for farmers and agricultural researchers by collecting imagery of croplands and other land cover over the Midwestern states during the growing season.
Unlike the more familiar handheld digital camera photographs taken by astronauts from the space station for the Crew Earth Observations experiment, ISSAC imagery is similar to multispectral data collected by the ASTER sensor onboard the NASA Terra satellite. The ISSAC is also mounted in the Window Observational Research Facility, or WORF, and operates independently of the station crew.
The sensor system uses two digital still cameras equipped with filters to collect individual image frames sensitive to the visible green, visible red, and near-infrared wavelengths of the electromagnetic spectrum. The individual frames are then combined to form a single multispectral (three-band) image. This wavelength combination makes the ISSAC particularly good at distinguishing different kinds of vegetation and detecting changes in the areal coverage and health of plants, two factors of importance for agricultural studies and monitoring.
In addition, the ISSAC can collect imagery of natural hazards and disasters in support of NASA humanitarian efforts. ISSAC demonstrated this capability soon after it became operational by collecting images of flooding from the Souris River near Minot, N.D., on June 24, 2011. Because ISSAC imagery is recorded in wavelengths similar to Landsat, scientists could easily compare the ISSAC data with earlier Landsat data of the Souris River valley, clearly illustrating the extent of flooding in and around Minot.
With the ISSAC now operational, data collected from the space station includes imagery that is similar to that acquired by polar-orbiting, satellite-based sensors. ISSAC significantly augments the traditional Earth observations from polar-orbiting satellites by collecting data at variable times of day and with different repeat frequencies.
Addition of the ISSAC and other remote sensing systems to the station, whether housed internally in the WORF or mounted externally, improves the capability of NASA to observe and monitor natural and anthropogenic (of human origin) Earth processes and natural hazards.
William L. Stefanov
Science Applications, Research and Development Department, Jacobs
