ARGOS (satellite) - Payloads

Payloads

"ARGOS will be the largest and most sophisticated research and development satellite Boeing has ever orbited for the Air Force," said Mr Will Hampton, Boeing director of U.S. Air Force Delta Programs.

Experiment (DOD Selective Experiments Review Board Year-Rank/Sponsor):

• CERTO - Coherent Electromagnetic Radio Tomography Experiment (1996-18/NRL) instrumentation, developed by NRL's Plasma Physics Division, consists of a stable radio beacon transmitter on the satellite and a chain of receivers on the ground. Radio transmissions from the CERTO beacon are processed by the ground receivers to produce two-dimensional maps of the electron densities in the ionosphere. The CERTO measurement technique provides images of the ionosphere with 10 km vertical and horizontal resolution. In addition, ionospheric irregularities of 1 km or less in size can be determined by fluctuations in the CERTO radio waves. CERTO can also be used to calibrate the ionospheric densities obtained using the EUV instruments such as HIRAAS, GIMI, and EUVIP on ARGOS. The CERTO radio-based technique has the advantage of higher spatial resolution than provided by the EUV-based techniques, but requires ground-based receivers aligned under the satellite orbit. The two techniques together on the same satellite provide substantial improvements over each technique separately. CERTO principal investigator, Dr. Paul Bernhardt notes that the NRL instruments on ARGOS will be the first demonstration combining EUV and radio sensors for enhanced imaging of the ionosphere.

• CIV - Critical Ionization Velocity Experiment (1990-9/AFRL-Kirtland AFB) Release of xenon and carbon dioxide gases from nozzles on the ARGOS orbiting with a velocity of about 7.4 km/s at an altitude of about 800 km is proposed. The releases will be conducted mostly in darkness over the Maui telescope site. The vector sum of the satellite and gas velocities will exceed the velocity requirement for the critical ionization velocity (CIV) process of xenon. It is feasible that the xenon gas will achieve critical velocity ionization. Associative ionization and collisional stripping will not occur for the xenon gas and there is no photo-ionization in darkness; ionization processes competing with CIV are absent. Neutral density, ambient magnetic field, and seed ionization effects on the xenon gas CIV will be discussed. Unlike xenon, carbon dioxide will not undergo CIV because of its higher velocity requirement. However, it is feasible that carbon dioxide colliding with the atmospheric species will form excited CO and OH molecules, which will radiate subsequently. Optical, IR, and UV observations on the satellite and at Maui Optical Telescope will provide diagnostic measurements for the experiment.

• ESEX - Electric Propulsion Space Experiment (1990-13/AFRL-Edwards AFB): an effort by the Air Force Research Laboratory’s Propulsion Directorate (Edwards AFB, CA) demonstrated a high-powered electric propulsion provided by a 26 kilowatt ammonia fueled arcjet. Its use in space and evaluate its performance and interactions with other experiments and spacecraft systems on board a satellite. Through the ionizing of ammonia, ESEX's electric propulsion was expected to double the payload-to-orbit capability of current space propulsion systems. The ammonia propellant consumed was four times less than the best performing chemical rocket engine in use at that time. For the team, the best information gathered was the validation that firing the highest powered electric propulsion system in space did not interrupt telemetry or affect other equipment on the spacecraft.

• EUVIP - Extreme Ultraviolet Imaging Photometer Experiment (1990-8/Army Space & Strategic Defense Command) will establish the behavior of the upper atmosphere and plasmasphere needed for Army secure communication systems design, prediction of magnetic storms, and characterization of the aurora.

• GIMI - Global Imaging Monitor of the Ionosphere Experiment (1990-19/NRL) will obtain wide-field FUV/EUV images of ionospheric and upper atmospheric emissions simultaneously, covering large areas of the earth from a low-earth orbit. These images will be used to determine chemical densities on a global basis and to detect disturbances in the ionosphere that are caused by auroral activity, gravity waves and foreign materials from meteors, suspected "ice comets," rocket exhausts and chemical releases. In between the atmospheric observations, GIMI will also perform an all-sky survey of stars and celestial diffuse sources at far-ultraviolet wavelengths. The GIMI instrument has two coaligned cameras for simultaneous observations of selected targets. Camera 1, which is sensitive in the 75-110 nm range, will primarily be used for observations of the dayside ionosphere, auroras, and stellar occultations, and for star field surveys. Camera 2 is sensitive in the 131-160 and 131-200 nm far-UV wavelength ranges and will be used for observations of the nightside ionosphere, airglow, stellar occultations, star field surveys, and also gas releases and rocket plumes at night.

• HIRAAS - High Resolution Airglow/Aurora Spectrograph Experiment (1990-5/NRL) is a multi-instrument experiment that will scan the edge of the Earth's atmosphere (called the limb) about every 90 seconds to measure naturally-occurring airglow missions in the 50 to 340 nanometer (nm) wavelength range over a wide array of geophysical conditions and at varying local times. The instruments will perform continuous observations over several spectral bands with resolution up to ten times better than with previous experiments. These measurements will be used to infer the composition (O+, N2, O, and O2) and temperature. Data from the HIRAAS experiment will be used to explore new concepts in monitoring space weather from satellites, and to improve high frequency communications and over-the-horizon radar, which rely on propagation through the atmosphere. The measurements will also help researchers assess the long-term effects of the increases of atmospheric greenhouse gases on the upper atmosphere and ionosphere.

• HTSSE II - High Temperature Superconductivity Space Experiment (1992-2/NRL): developed by the Naval Research Laboratory will space qualify superconducting digital subsystems that could offer factors of 100 to 1000 in power reduction - more than ten times higher speed and similar weight reduction, than today's silicon or gallium arsenide (GaAs) based electronics. Spacecraft designers will evaluate the benefits for future systems.

• SPADUS - Space Dust Experiment (1990-33/Office of Naval Research) sponsored by the University of Chicago with funding by the Office of Naval Research, will measure velocity and impact of dust in space orbit.

• USA - Unconventional Stellar Aspect (1990-22/NRL) - Sponsored by Naval Research Lab, Space Science Division, the USA experiment was designed to observe bright x-ray sources, mostly binary star systems, including a black hole, a neutron star, or a white dwarf, orbiting with a more typical star. In neutron stars, gravity has compressed matter down to densities larger than those found in the nucleus of an atom. In all of these types of binary systems, extraordinarily strong, relativistic gravitational forces and enormous magnetic fields act in concert to produce dramatic phenomena not observable from Earth-based laboratories. In addition to providing valuable new information for astrophysicists and particle physicists, USA has been designed to make significant contributions to applied science, environmental science, and engineering research. It will use x-ray sources to test new approaches to satellite navigation and to conduct the first tomographic survey of Earth's atmosphere. It will also test new concepts for making spacecraft computers more reliable, an approach called fault-tolerant computing. Finally, a unique feature of USA is that photon events are time tagged by reference to an onboard GPS receiver allowing precise absolute time and location determination. USA operated from May 1, 1999 through November 16, 2000.