ObsReduce Upgrade History

ObsReduce 1.2.4

Bug Fixed

Version 1.2.4 corrected a serious error in versions 1.1 and 1.2, affecting the reduction of three-star appulses, which resulted in the miss-distance being computed as a fraction of the separation between stars A and B, instead of stars B and C. This affected every single three-star appulse reduction.

ObsReduce 1.2

Stopwatch Support

Version 1.2 introduced the option to enter observation times as elapsed stopwatch times, including provision to compensate for the rate of drift, as described in section D.5 of the manual.

Wider Field of View

Version 1.2 doubled the maximum diameter of the FOV to 20 deg. This is intended to facilitate those rare cases, when a bright satellite, seen with the unaided eye, is measured against very widely spaced stars.

Bugs Fixed

- eliminated the large jumps in position that occurred when using the Move Satellite spin buttons, when the field of view was set to its maximum size

- eliminated a small error in the displayed satellite track, that was noticeable when the diameter of the field of view was very small

ObsReduce 1.1

Version 1.1 introduced two enhancements to the reduction of appulses (satellite passing near a single star).

The program now automatically estimates the position angle, based upon a satellite's existing orbital elements. It also supports the use of up to two stars in addition to the appulsed star for the purpose of estimating the miss-distance. These new features are described in sections D.9.1.3 and D.8 of the manual.

ObsReduce 1.0.3

Version 1.0.3 was mostly a bug-fix, plus a few minor new features:

Bugs Fixed

- corrected an error in the formatting of the declination of UK position format 2. I had mistakenly allowed as many as two significant places after the decimal, even though the standard allows only one. This caused the dec to encroach upon the positional uncertainty field, making a mess of it. Corrected in version 1.0.1.

- corrected a serious error in the design of the appulse-reduction routine, such that the position of the appulsed star was being computed for the time corresponding to the centre of the FOV display, instead of the observation time. When displaying a satellite's predicted track, it is normal for the FOV time to be slightly different than the observation time. If the elset is greatly outdated, then the time difference can become quite large. The greater the difference between the FOV time and the observation time, the greater the error in the reduction, caused by the bug. Testing of the bug indicated that for time differences of at least several seconds, there is no error at all in appulse reductions. Corrected in version 1.0.2, released to only a handful of users until now.

- corrected a frequent annoyance in which the program entered a loop in which it insisted that two stars be selected, despite the user's intentions. In order to exit the loop, the user had to select two stars, then de-select them.

New/Improved Features

- enables the addition of stars missing from the database, as well as planets and asteroids, as explained in Section D.23 of the manual.

- when two stars have been selected, their angular separation is displayed immediately in the Star Sep box, at the lower left of the program's display. Useful when pre-selecting reference stars in advance of observing; or when reducing appulses, in which the miss-distance was estimated as a fraction of the separation between a nearby pair of stars.

- the program displays an estimate of the prediction time uncertainty of the elements used to compute a satellite's track, as explained in Section D.13 of the manual.

- the SDP4 orbit propagator has been modified to retain deep space perturbations at epoch, in conformance with a change believed to have been made long ago by USSTRATCOM.