The Earth Observer, May/June, 1995 Issue

Ames Research Center: A Complete Service Center for Airborne Earth Observation

Jeff Jenner (Jeff_Jenner@qmgate.arc.nasa.gov), Medium Altitude Missions Branch, NASA Ames Research Center

For more than 20 years, NASA Ames Research Center has provided a variety of aircraft platforms for Earth observations. Currently, Ames operates six airplanes, which form a fleet that can carry remote sensing and in situ instruments to altitudes as high as 70,000 feet and take them virtually anywhere in the world. The Ames fleet supports a wide range of studies--from small, inexpensive, single-investigator, "quick-look," experiments, to detailed, long-term, multi-aircraft research programs. The fleet carries investigators from NASA, other federal agencies, academic institutions, and international scientific organizations. Experiments conducted on Ames aircraft have made important contributions to the fields of geophysics, meteorology, atmospheric science, earth resources, geology, volcanology, and hydrology. Several experimental and developmental remote sensing instruments that were tested on Ames airplanes have eventually flown on satellites. Ames aircraft have also played key roles in disaster relief efforts and assessments.

Virtually all of the ground facilities required to design, build, and integrate the flight experiment hardware; calibrate remote sensing instruments; provide finished data products; and maintain the aircraft are located within walking distance of the main hangar. Also, much of the mission-critical support hardware is portable and is routinely deployed to remote sites around the world. Ames aircraft operations teams have established a long and distinguished record of service to the Earth science research community, continuously working towards their goal of "anytime, anyplace, anywhere."

The DC-8 Airborne Laboratory is a medium-altitude airplane, powered by four CFM-56 high-bypass turbofan jet engines. It can carry a payload of up to 30,000 pounds to cruising altitudes as high as 41,000 feet, with a range of more than 5,000 nautical miles. It has seated as many as 30 scientists working on 14 different experiments. Cruise speed is 425-490 knots True Air Speed.

Although it has no "core" instruments (those operated and maintained by Ames personnel), the DC-8 has a wide array of experiment support systems, including an inertial navigation system, a Global Positioning System (GPS) receiver, a Precision Thermal Radiometer, weather radar, hygrometer, radar altimeter, and weather facsimile. A Data Acquisition and Distribution System (DADS) records airplane navigation and environmental data and distributes it to the experimenter workstations. The DC-8 has seventeen large-aperture viewports (facing four different directions) that can accommodate windows up to 16 inches in diameter or plates with air sampling probes. It can also be equipped with an ejection system to release standard radiosondes, which relay atmospheric conditions to a receiver on the airplane as they parachute to the surface.

The DC-8 has true global-reach capability and is routinely deployed internationally. It has flown over both the North and South Poles; the Atlantic, Pacific, and Arctic Oceans; and all seven continents. Notable DC-8 airborne research programs are the Ozone Hole studies in the Arctic and Antarctic. It played a key role in quantifying the extent of the Ozone Holes and measuring atmospheric conditions that were thought to cause it. The DC-8 carried the Jet Propulsion Laboratory (JPL) L-, P-, and C-Band Synthetic Aperture Radar (SAR) systems to gather data on radar calibration sites in the United States, Canada, Europe, and Australia. JPL investigators and Earth scientists used this information to validate data from the Space Shuttle Imaging Radar missions. JPL investigators continue to use the airplane to test new concepts and to develop new techniques for SAR imaging. Atmospheric chemistry experiments conducted on the DC-8 have significantly increased our knowledge of the troposphere and how it is changing in response to human activity. Current experiments involve lidar (light detection and ranging), which is an effective tool for ocean and atmosphere pollution measurements.

The C-130 Earth Resources Aircraft is a low- and medium-altitude, moderate-speed airplane with a payload capacity of 20,000 pounds. It cruises at speeds between 150 and 300 knots and can reach altitudes to 31,000 feet. The C-130 has been extensively modified to include nadir and zenith viewports and can accommodate instruments that extend out over the edge of the aft cargo ramp. It can support a wide variety of onboard sensors, including multi-spectral scanners, radiometers, air sampling equipment, and aerial cameras. The Ames core instruments include:

Another instrument that is carried on most C-130 flights is the Thermal Infrared Multi-spectral Scanner (TIMS). Geologists use its six discrete channels in the thermal infrared band extensively for rock type discrimination. Volcanologists use TIMS for temperature distribution measurements in volcanoes.

Although it primarily flies within the Continental United States and Canada, the C-130 has been deployed to sites as far away as Niger, Australia, and Germany. It has also served as a rapid response observation platform during local disasters such as the Oakland Firestorm (1990), the Malibu fires (1993), the Los Angeles Earthquake (1994), and the Northern California floods (1995). During the Malibu fires, for example, the near-infrared and thermal-infrared scanners penetrated the smoke and revealed the extent of the damage and locations of hot spots. A standard VHS videotape of the imagery was delivered to police and fire authorities at the airport minutes after acquiring the data.

The Learjet Airborne Observatory is a Model 24 Corporate Class, medium-altitude, high-performance airplane with a range of 1500 nautical miles, a ceiling of 45,000 feet, and a payload capacity of 1,200 pounds. Cruise speed is 450 knots True Air Speed. An optional long-range fuel tank allows the Learjet to be deployed worldwide. It supports research in astrophysics, meteorology, planetary and atmospheric science, geophysics, and reduced gravity (parabolic flight). The primary observation instrument is a clear-aperture, gyro-stabilized, open-port, 30-cm infrared telescope that looks out the left side of the airplane.

An infrared camera carried on the Learjet recently photographed the engine exhaust plume from the Boeing 747 Shuttle Carrier Aircraft while the two airplanes were flying in formation. Post-flight analysis confirmed that background heat from the exhaust plume would have only marginal science impact on the proposed Stratospheric Observatory For Infrared Astronomy (SOFIA), which will be flown aboard a 747 at the end of the decade. This initial research has led to the proposal for the NASA Infrared Measurement System (NAIMS), which would permit in-flight imaging and spectral measurement of airborne targets. The Learjet has also been used for parabolic flight experiments, providing reduced gravity conditions for 20 to 30 seconds at a time, for a total of six events per flight.

The ER-2 High Altitude Research Aircraft carries a single pilot and up to 2600 pounds of payload to altitudes approaching 70,000 feet. It is a modified version of the U-2 aerial reconnaissance airplane. Ames currently operates three ER-2s, which support stratospheric and tropospheric chemistry experiments, remote sensing, geographic mapping, disaster assessment, and preliminary testing of spacecraft sensors. A typical mission lasts up to six-and-one-half hours and covers 2,200 nautical miles. Under certain conditions, it is possible to extend this to eight hours and 3,000 nautical miles. The maximum-altitude mission profile involves a steady climb from 60,000 feet to 70,000 at a constant mach number.

The ER-2 has flown over many areas of the globe, from the North Pole to the tropical Western Pacific to Antarctica. Each year, the ER-2 program conducts data collection flights for 40-50 individual scientists as well as for large multi-instrument research programs involving teams of scientists. Experiment objectives range from atmospheric sampling to simulations of spacecraft sensor observations.

The ER-2 is equipped with an Inertial Navigation System that can get position updates from an on-board GPS receiver. It also has a data recording and distribution system that records aircraft performance and navigation data and distributes it to each of the payload areas. The ER-2 core instruments include:

In 1994, one ER-2 participated in an eight-month study that examined the causes of the ozone loss in the southern hemisphere. Based primarily at Christchurch, New Zealand, it flew forty-five air sampling missions over Antarctica, including the first sampling of the exhaust from the supersonic passenger jet Concorde (Air France). Over the past eight years, air samples gathered by the ER-2 have played a key role in determining the chemical reactions thought to cause ozone depletion in the upper atmosphere.

When deployed to airfields around the world, Ames airplanes and their crews are highly visible representatives of NASA and the United States. Local residents often come out to see the airplanes and, when feasible, tour them. The airplanes also attract members of the news media; some flight crew members give several interviews a day regarding the airplanes and their missions. This not only helps promote NASA, but provides many opportunities to increase the public's general awareness of remote sensing and the environment. At the working level, Ames flight crews routinely participate in multi-national, multi-aircraft field campaigns.

Educational outreach is a basic Ames mission and an important part of our operations. Recently, the C-130 carried a crew of graduate geology students during flights over Arizona, which resulted in several graduate research papers. The accessibility of the C-130 (with its relatively constant suite of instruments and local operation), together with the growing interest of K-12 teachers in remote sensing, also provides an opportunity for teacher involvement. Such a program would draw on the experience of the highly successful Ames C-141 Kuiper Airborne Observatory Flight Opportunities for Science Teacher Enrichment (FOSTER) program.

Routine aircraft maintenance and repair is done in-house, with oversight from Ames Quality Control and Airworthiness personnel. Mission-peculiar hardware is fabricated by personnel from the sheet metal, machine, and model shops adjacent to the main hangar. A dedicated engineering staff designs and analyzes mission-peculiar hardware for many airborne science and Earth observation customers. Ames maintains calibration laboratories for many of the common remote sensing instruments and sensors.

All mission-related activities (including hardware design and fabrication) are coordinated by the members of the aircraft mission management offices. These mission managers also fly with the experiments (except in the ER-2) and provide interfaces between the flight crews and experimenters. Our on-site Aircraft Data Management Facility produces customized, finished images or magnetic tapes in a format readable by the customers' equipment. The Data Facility personnel assist many investigators in imagery interpretation and image format variations. Our film processing lab provides film developing services and finished aerial photographs.

Ames Earth science aircraft continuously receive hardware upgrades or modifications that keep them up-to-date with the needs of the research community and developments in the remote sensing industry. The DC-8 recently received a new Navigation Management System (NMS), which allows pilots to navigate using a combination of data from the Global Positioning System (GPS) and Distance Measuring Equipment (DME). Flight tests showed that the NMS can determine the airplane𨤳 true position to within 100 feet.

The C-130 will soon be capable of carrying the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). AVIRIS was developed by JPL and is the first operational hyper-spectral instrument. It is unique in that it can produce imagery in 224 discrete bands over the spectral range from 0.38 痠 to 2.5 痠. The result is high spectral resolution as well as high spatial resolution, which greatly increases the scientific utility of the data and the probability of accurate interpretation of objects in the imagery. Hyper-spectral imaging is on the edge of commercial acceptance, but its progress is presently impeded by the lack of satellite-based hyperspectral sensors and high demand for the few airplanes that can carry them. Extending the C-130's capability to include hyper-spectral imaging would make this tool more accessible and may promote the development of many new commercial applications.

The Learjet was recently modified to carry the Airborne Infrared Disaster Assessment System (AIRDAS). AIRDAS is an innovative multispectral scanner that was designed and built at Ames using seed money from the Center Director's Discretionary Fund and the U.S. Forest Service Fire Research Laboratory. It is the only airborne instrument that can resolve high-temperature profiles in wild fires, thus allowing accurate measurement of fire intensities. The downward-looking port installed for AIRDAS can accommodate other instruments, such as aerial cameras and electro-optical sensors. The Learjet also has a new GPS receiver that can provide position data to experiment systems.

The ER-2 is being outfitted with Starlink, which should be operational by the end of 1995. Starlink uses the NASA Tracking and Data Relay Satellite System (TDRSS) to communicate with investigators on the ground. This new system will increase the ER-2's real-time data transmission capacity from 1.2 megabits per second with a range of 275 miles from a ground station to 274 megabits per second from virtually anywhere in the world. Starlink will also add an uplink capacity of 200 kilobits per second. The global coverage from the TDRSS will provide opportunities to reduce the amount of ground support hardware required for remote deployments.

Remote sensing of the Earth is a rapidly growing industry world-wide. The Ames Earth Science Aircraft Program, with its extensive experience in remote sensing, has the opportunity to play a key role in developing this fledgling industry--thereby helping to maintain U.S. leadership in it. Today, the primary challenge in remotely sensed data is to turn it into useful information. This will require adequate data storage and computer systems capable of managing, organizing, sorting, distributing, and manipulating the data at exceptional speeds. With its close proximity to Global Positioning System equipment companies, computer hardware manufacturers, and software developers, Ames is in a unique position to lead the integration of information systems with multispectral imaging scanners. Our current development efforts include a method to automatically combine GPS position information with data from multispectral imaging scanners. If successful, this system will eliminate the need for manual georectification, or "stretching," of most digital imagery (georectification makes an image geometrically correct with respect to corresponding points on maps of the terrain).

The aircraft mission management group is currently leading several efforts to increase the number of reimbursable flight projects. We hope to achieve a better balance between NASA-funded and reimbursable projects, in order to get the most from our aircraft resources. In reimbursable projects, non-NASA organizations pay for the use of NASA facilities to develop new and innovative remote sensing applications. These projects are performed such that they do not interfere with NASA-funded projects and typically involve research that will benefit NASA in some way. For example, the City of Scottsdale, Arizona, recently funded a C-130 flight to acquire multi-spectral and thermal infrared imagery of Lake Havasu, in an attempt to locate possible sources of high bacterial counts in the water.

Increasing awareness of remote sensing among state and local natural resource managers is creating many new opportunities to develop new and innovative applications. We are planning a series of technology demonstration flights for the San Francisco Bay Area Air Quality Management District (BAAQMD) to determine whether or not airborne thermal infrared imagery will provide a reliable and economical method of determining the density and spatial distribution of lit residential fireplaces. The BAAQMD wants to quantify the contribution of residential wood burning to the overall airborne particulate concentration. The ability of the C-130 to image a large portion of the Bay Area in a few hours will permit meaningful correlation with airborne particulate measurements made during the same timeframe. We also plan to create a standard briefing package and remote sensing applications handbook targeted at potential customers who could benefit from remote sensing but know little or nothing about it.

Our goal at Ames is to provide low-cost, high-quality, world-class airborne science research platforms with "global reach" capability. We are continuously reviewing the needs of the Earth science research community as well as our own capabilities and making the upgrades and changes necessary to achieve that goal. These improvement efforts will also help to ensure that our programs continue to follow NASA's overarching philosophies of informational and educational outreach and local relevance.

Although NASA-sponsored research takes priority, Ames airplanes perform research for other public agencies and private organizations on a cost-reimbursable basis. The primary criteria for reimbursable programs are that their objectives are consistent with NASA's mission of developing new or innovative methods and capabilities in airborne science. Investigators who want to use Ames aircraft can do so by submitting a Flight Request Form (OM-7) with the following information, as a minimum:

The Ames C-130B has now been grounded by the Office of Mission to Planet Earth, NASA Headquarters, but a Wallops C-130Q will continue to be available to meet the scientific requirements of low- and medium-altitude remote sensing.
--Ed.