SeaTrack: Ground station orbit prediction and planning software for sea-viewing satellites

An orbit prediction software package (Sea Track) was designed to assist High Resolution Picture Transmission (HRPT) stations in the acquisition of direct broadcast data from sea-viewing spacecraft. Such spacecraft will be common in the near future, with the launch of the Sea viewing Wide Field-of-view Sensor (SeaWiFS) in 1994, along with the continued Advanced Very High Resolution Radiometer (AVHRR) series on NOAA platforms. The Brouwer-Lyddane model was chosen for orbit prediction because it meets the needs of HRPT tracking accuracies, provided orbital elements can be obtained frequently (up to within 1 week). Sea Track requires elements from the U.S. Space Command (NORAD Two-Line Elements) for the satellite's initial position. Updated Two-Line Elements are routinely available from many electronic sources (some are listed in the Appendix). Sea Track is a menu-driven program that allows users to alter input and output formats. The propagation period is entered by a start date and end date with times in either Greenwich Mean Time (GMT) or local time. Antenna pointing information is provided in tabular form and includes azimuth/elevation pointing angles, sub-satellite longitude/latitude, acquisition of signal (AOS), loss of signal (LOS), pass orbit number, and other pertinent pointing information. One version of Sea Track (non-graphical) allows operation under DOS (for IBM-compatible personal computers) and UNIX (for Sun and Silicon Graphics workstations). A second, graphical, version displays orbit tracks, and azimuth-elevation for IBM-compatible PC's, but requires a VGA card and Microsoft FORTRAN

SeaWiFS technical report series. Volume 11: Analysis of selected orbit propagation models for the SeaWiFS mission

An analysis of orbit propagation models was performed by the Mission Operations element of the Sea-viewing Wide Field-of-View Sensor (SeaWiFS) Project, which has overall responsibility for the instrument scheduling. The orbit propagators selected for this analysis are widely available general perturbations models. The analysis includes both absolute accuracy determination and comparisons of different versions of the models. The results show that all of the models tested meet accuracy requirements for scheduling and data acquisition purposes. For internal Project use the SGP4 propagator, developed by the North American Air Defense (NORAD) Command, has been selected. This model includes atmospheric drag effects and, therefore, provides better accuracy. For High Resolution Picture Transmission (HRPT) ground stations, which have less stringent accuracy requirements, the publicly available Brouwer-Lyddane models are recommended. The SeaWiFS Project will make available portable source code for a version of this model developed by the Data Capture Facility (DCF)

SATELLITE TELEMETRY REVEALS WINTER HOME OF EURASIAN CRANE FROM NORTHWESTERN SIBERIA

Satellite telemetry is a developing technology for the study of crane migration. A greater sandhill crane (Grus canadensis tabida) was tracked by satellite from Florida to Michigan in March 1989 (Nagendran 1992). This note reports the second attempt to use satellite telemetry to follow crane migration. In 1989 -90, tests of various harness and backpack designs for satellite telemetry transmitters (PTT\u27s) with free-flying and confined sandhill cranes led to a 4-strap design (see Olsen et al. 1992) that was accepted for field testing. Through a cooperative effort between the Patuxent Wildlife Research Center (USFWS) , International Crane Foundation, Soviet Nature Conservation and Reserves (USSR), aka State Reserve (Russia), and the National Aeronautics and Space Administration (USA), 3 battery-powered PTT\u27s (weight 161-163 g plus 15 g for harness) manufactured by Telonics (mention does not constitute U.S. Government endorsement) were placed on 1 adult female and 2 adult male Eurasian cranes (G. grus) in the Kunovat Basin in northwestern Siberia in June 1990. The 2 males were captured by using alpha-chloralose-laced sandpiper (Tringa sp.) eggs; the female, then in full wing molt, was captured on foot after helicopter pursuit (see Ellis and Markin 1991 for capture details). Data from System Argos revealed that all 3 birds remained on their territories through the summer. In mid- to late-August. all 3 moved west or southwest to the marshes immediately adjacent to the Ob River. They remained there about 1 month, then proc~eded south parallel to the Ob. One of the 2 males was still mobile when his transmitter went off the air in the Tyumen region 1,038 km from his summer home. The second male traveled 778 lan, but after 20 September his PTT remained stationary (backpack removed or crane dead) until 25 December when the last signal was received. During the last half of October, the female continued south-southwest through Kazakhstan, Uzbekistan, and Turkmenistan. Between 11 and 14 November, she arrived at her wintering area along the Hari River on the Afghan-Iranian border, 3,370 km from her summer home. She and her PTT remained active until the last reception on 23 February 1991. Because the PIT\u27s were programmed to transmit intermittently (to extend battery life), rates of travel are normally known only over periods of days or weeks. However, 1 male, monitored in flight over a 5-hour period, traveled 164 kID (33 kmlhr). The other male traveled 748 kID over a 4-d.ay period. Over a very long stage (1,900 km in 16 days) across Central Asia, the female averaged 116 km/day