Summary   Overview     Benefits     Contacts


The New Millennium Program's Earth Observing-1 (EO-1) mission is providing for the on-orbit demonstration of a high data rate, low mass X-Band Phased Array Antenna (XPAA) for down-linking imaged data from the EO-1 solid state recorder. The XPAA offers significant benefits over current mechanically pointed parabolic antennas, including the elimination of deployable structures, moving parts, and the torque disturbances that moving antennas impart to the spacecraft.


The XPAA is composed of a flat grid of 64 radiating elements whose transmitted signals are combined spatially to produce the desired antenna directivity. The phases of each of the radiating elements are varied by computer to point the beam in the desired direction. For the EO-1 mission, the radiating elements are combined with low power, high efficiency solid state amplifiers to achieve the required radio frequency power level. The antenna is mounted on the Earth-facing side of the spacecraft to allow communications with ground stations. The antenna's mass is 5.5 kilograms. It has an Effective Isotropic Radiated Power (EIRP) of approximately 160 watts, and transmits data at 105 megabits per second. Boeing Phantom Works, located in Seattle, WA, developed the antenna for GSFC.
Future generations of Earth Science missions will generate terabytes of data daily which must be returned to Earth. The XPAA provides a low cost, low mass, highly reliable means of transmitting hundreds of megabits per second to low cost ground terminals. The XPAA also has the inherent advantage of providing a body-fixed design which can allow simultaneous capture and transmission of data, avoiding perturbations to instrument measurements.

Ken Perko
NASA's Goddard Space Flight Center
Mail Code: 567
Phone: (301) 286-6375 Email:
Kenneth.L.Perko.1@gsfc.nasa.gov

Nick Speciale
EO-1 Mission Technologist
NASA's Goddard Space Flight Center
Mail Code: 490
Phone (301) 286-8704
Email: Nicholas.J.Speciale.1@gsfc.nasa.gov