Degree Inclination Orbit Research Articles

Strategy for Active Debris Removal Using Electrodynamic Tether

In this study, the active removal of space debris is studied from the point of view of technological feasibility. First, the actual debris distribution is analyzed to determine which debris objects should be removed considering the effectiveness in preventing collisional cascading and feasibility such as the delta-V required for rendezvous with the objects. Target regions such as sun-synchronous orbit and a 1,000km altitude, 83 degree inclination orbit are then selected and rendezvous with debris object in these regions are studied. Electrodynamic tether is promising as a highly-efficient propulsion system required for debris de-orbit in these regions. A small piggyback-launched satellite to dispose of one debris object, and a dedicated debris removal satellite which removes several debris objects from crowded regions are proposed. Precise numerical simulations of EDT are performed to evaluate the de-orbit time.

Proton Flux Anisotropy in Low Earth Orbit

Proton flux anisotropy as a function of altitude in the South Atlantic Anomaly is investigated using data from the Compact Environment Anomaly Sensor (CEASE) flown onboard the tri-service experiment-5 (TSX-5) satellite from June 2000 to July 2006. In a 410 km times 1710 km, 69 degree inclination orbit, TSX-5 spanned a broad range of the low Earth orbit regime. Using measurements of total dose, integral energy flux >40 MeV and the differential flux at 40 MeV sorted into 3 degree latitude times 3 degree longitude times 50 km altitide bins and averaged over the entire mission, the components arising from eastward and westward traveling protons have been determined in areas of the SAA where CEASE detection efficiency is not compromised. For the first time, ratios of these components have been compared to predictions of east-west effect models above 400 km. There is good agreement in general with the anisotropy becoming apparent at approximately 1200 km (moving down) and increasing rapidly starting at approximately 1000 km, the magnitude and rate depending on location within the anomaly. Measurements of the differential flux at 40 MeV are compared to predictions of standard radiation belt models as a function of altitude and found to be substantially higher in magnitude than AP8, though a comprehensive survey has not yet been performed.

NASA/International small satellite program

After seven successive launch date changes because of the ARGOs mission readiness and after nine launch attempts, both Oersted and SUNSAT were successfully deployed (after a special Delta-II maneuver) into an 857 km × 655 km, 96.47 degree inclination orbit on February 23, 1999. This is very close to the orbit requested by Oersted/SUNSAT and the missions began on a very positive note. Six weeks after launch both Oersted and SUNSAT were successfully checked out with only minor anomalies and the scientific phase of the programs beganin April 1999. Oersted is still functuioning as designed and continues to produce valuable scientific data on the Earth's magnetic field that is often coordinated with similar instruments on the German CHAMP and the Argentine Sateliete De Apliocaciones Cienificas (SAC-C) missions. SUNSAT produced data for two years (design life was one year) and ceased to transmit in January 2001. SAC-C was launched into a 705 km sun synchronous orbit as a dual payload with the NASA EO-1 mission in November 2000. The principal mission of SAC-C is to utilize a five band camera for Earth observation.

Characteristics of the LAGEOS and ETALON satellites orbits

Satellite Laser Ranging (SLR) data to retroreflector carrying satellites allow the derivation of the details of their orbital evolution and behavioral characteristics. The semi-major axis monitors the effect of non-conservative forces, and the eccentricity is particularly affected by solar radiation pressure. The conservative forces of the geopotential and Earth and ocean tides influence the behavior of the inclination and the right ascension of the ascending node. The contrasting effects of these perturbations on the long-term evolution of the satellites LAGEOS I (circular, 12,000 km semi-major axis, 109 degree inclination orbit) and LAGEOS II (circular, 12,000 km semi-major axis, 53 degree inclination orbit), as well as ETALON I and ETALON II (both of which are in circular, 25,500 km semi-major axis 65 degree inclination orbits) will be presented. The major difference between the evolution of the LAGEOS satellites' orbits is caused by the difference in inclinations between LAGEOS I and LAGEOS II. There is no such contrast in the orbits of ETALON I and II and the observed dissimilarity in their response to direct solar radiation pressure must be caused by satellite area, mass or reflectivity differences. Although both LAGEOS satellites have observed solar radiation coefficients of about 1.13, using a 42 cm radius and a mass of 1346 kg for the ETALON satellites, the coefficient of solar radiation pressure for ETALON I has been determined to be 1.22, and 1.25 for ETALON II. The capability of these satellites to define a reference frame for Earth orientation measurements will improve with the models for their orbital evolution.

Trapped heavy ions on LDEF

Plastic nuclear track detectors were used to study below-cutoff heavy ions in a 28.5 degree inclination orbit aboard the NASA satellite Long Duration Exposure Facility (LDEF). Particle arrival directions and energy spectra were measured in stacks of CR-39 and cellulose nitrate. The obtained results for particles with energies below 50 MeV/nuc are interpreted as evidence for the detection of a trapped component registered in the South Atlantic region at values of L = 1.4−1.7.

Measurements on the Shuttle of the LET Spectra of Galactic Cosmic Radiation and Comparison with the Radiation Transport Model

A new class of tissue-equivalent proportional counters has been flown on two space shuttle flights. These detectors and their associated electronics cover a lineal energy range from 0.4 to 1250 keV/microns with a multichannel analyzer resolution of 0.1 keV/microns from 0.4 to 20 keV/microns and 5 keV/microns from 20 to 1250 keV/microns. These detectors provide the most complete dynamic range and highest resolution of any technique currently in use. On one mission, one detector was mounted in the Shuttle payload bay and another older model in the mid-deck, thus providing information on the depth dependence of the lineal energy spectrum. A detailed comparison of the observed lineal energy and calculated LET spectra for galactic cosmic radiation shows that, although the radiation transport models provide a rather accurate description of the dose (+/- 15%) and equivalent dose (+/- 15%), the calculations significantly underestimate the frequency of events below about 100 keV/microns. This difference cannot be explained by the inclusion of the contribution of splash protons. The contribution of the secondary pions, kaons and electrons produced in the Shuttle shielding, if included in the radiation transport model, may explain these differences. There are also significant differences between the model predictions and observations above 140 keV/microns, particularly for 28.5 degrees inclination orbit.

LET Spectra in Low Earth Orbit

The Trapped Ions in Space (TRIS) experiment was flown on the Space Shuttle in October, 1984. It contained a stack of plastic track detectors that recorded linear energy transfer (LET) spectra behind various thicknesses of shielding in a 57 degree inclination orbit. A preliminary analysis of the data shows that behind shielding of at least 40 mils Al equivalent, the LET spectrum is dominated by galactic cosmic rays and the direct ionization of trapped protons and that it is reasonably well predicted by the CREME model. For a minimum shielding of approximately 4 mils Al equivalent, the measured LET flux exceeds the CREME predictions, especially at high LET. This is probably due to contributions from the products of proton-induced nuclear reactions in the detector and helium ions trapped in the inner radiation belt.