Regional aerogeophysical surveys can provide important information on crustal/lithospheric structure that is complementary to information obtained from seismic data. Recent small aircraft aerogeophysical programs in Antarctica have been very productive. However, the logistic costs and difficulty associated with establishing base camps and fuel dumps, and the relatively slow speeds and short range of Twin-Otter class aircraft preclude their use for continental-scale surveys. A long-range aircraft with a modern measurement suite including airborne gravity, magnetics, ice topography and ice-penetrating radar instrumentation, would be an important component of a comprehensive research program on the structure and evolution Antarctica. The NSF sponsored C-130 flights of the TUD radar and magnetometer systems in previous decades demonstrated the utility of this approach. More recent examples of long-range aerogeophysical measurement programs include: airborne gravity and magnetic surveys aboard NRL P-3 Orion over Greenland and the Arctic Ocean basins; ice topography and radar measurements over Greenland by the NASA P-3; and Arctic and Antarctic aerogeophysical measurements from the Russian IL-18. There are several approaches to acquiring a long-range aerogeophysical capability for Antarctic research. One is to utilize a ski capable aircraft like the LC-130. This allows routine operation from snow runways or even from unprepared sites at a cost in increased drag and reduced payload. Unfortunately, LC-130 aircraft are in extremely short supply and must be used to support Antarctic logistics. It is also very expensive to modify a C-130 airframe for radar antennas, magnetometer or down-looking instrumentation. Another possibility is the Basler modified DC-3. This aircraft is intermediate in range and payload between the Otter and LC-130, and cruise speed is relatively low, limiting the size of surveys. The use of long-range wheeled aircraft from blue-ice or sea-ice runways has also been extensively discussed. The major problem with wheeled aircraft operations is the lack of alternate landing sites for weather emergencies. However, Russia has considerable Antarctic experience with the IL-18, a large four-engine turboprop, including several flights from the McMurdo sea-ice runway. Wheeled C-130s have also been operated for several years to ferry personnel and equipment between Christchurch and McMurdo. During the transit to Antarctica, the wheeled C-130s have a window of about 3.3 hours after the point of safe return where they are committed to landing at McMurdo, with no available alternates. Decision matrices for weather conditions have been developed to permit safe operations during this "no-alternate" period. The Naval Research Laboratory has been investigating basing a research modified P-3 Orion (similar to the IL-18) from McMurdo for several years. A P-3 can fly more than six times farther in a single flight than a research configured Twin-Otter (4500-6000 km depending on altitude and fuel reserve requirements). This range makes many science targets within the Antarctic interior feasible from a McMurdo base. Operation from McMurdo provides significant logistic and cost advantages since there is no need to establish a base camp and fuel cache. This eliminates any requirement for LC-130 support and base-camp logistic personnel. The P-3 is also an excellent science platform. The aircraft was specifically designed as an aeromagnetics platform with a non-magnetic extended tail boom. The NRL P-3s have cargo interiors for easy installation of science equipment and a specially modified bomb-bay compartment for installation of down-looking sensors and antennas. In this configuration the P-3 has a scientific payload of more than 3000 kg and can carry up to 8 scientists in addition to the flight crew. UT and NRL have done a preliminary design analysis for the addition of RES antennas mounted fore-and-aft in a radome below the bomb-bay. This method permits installation of a coherent array of four to six antenna sections for beam-forming. It is also considerably less expensive than the wing-mounted antennas used on the C-130 or the NASA P-3. The NRL aircraft operations branch has recently determined that it is feasible to operate a P- 3 safely within a 3.3 hour transit of McMurdo under the existing wheeled C-130 decision matrix. This presently limits us to a 2000 km radius of operations. Future availability of white-ice (Pegasus), or blue-ice alternate runways may increase this distance. Analysis of historical weather data and discussions with personnel involved with airborne operations at McMurdo indicate that the P-3 should arrive at the sea-ice runway by October 15 and depart by the first week of December. The most effective use of the P-3 would be to schedule a 240 hour block of flight-time for a field season. Roughly 35-40 hours of transit (each way) are required to move the aircraft from the United States base to McMurdo and back. This would leave approximately 165 flight-hours of science operation from McMurdo. Flying 4-5 eight to nine hour flights per week would allow completion of 18 to 20 project flights from McMurdo in four weeks with a reserve for weather and maintenance problems.