Backtrack Orbit Search Algorithm - Technical Review Comments-1

PRIMARY ADDITIONS OR CHANGES:

• Appendix C - please provide a pointer to the source code (either URL or instructions on how to get the Spheres package). A test case including sample input and expected output would also be helpful.
• Can you provide a figure illustrating the general search problem Backtrack solves? (For example, show user's area of interest outlined on globe, easternmost and westernmost swaths that see some part of this area of interest, highlight line on equator indicating equatorial crossing range for orbits of interest). This could maybe go in section 6.
  • Or, if this is the intent of Appendix B, maybe in Section 6 you could refer readers to the appendix for an example.

MINOR EDITORIAL CHANGES:

• Throughout the document the word "orbit" is used to mean the subsatellite track on the earth's surface (i.e. "ground track"). This could lead to confusion and should be corrected.
• Section 6, first sentence - add "for a selected geolocation" to end of sentence.
• Section 7 figure needs a figure number and caption, and should be referenced in the text
• Section 8, end of second paragraph - "Backtracks" should be "Backtrack's"
• Section 8, last paragraph - seems to be missing an introductory clause - is this the statement of the problem the algorithm solves?
• Section 8.1, second sentence - needs "equator" before "crossing"
• Section 8.2, descriptions in second paragraph (starting "First consider") need some clarification. Some suggestions:
  • reference a figure
  • add to second sentence "...construct a great circle that approximates the satellite's orbit over the point of interest"
  • the phrase "point intersect at the point" doesn't make sense
  • in the next sentence please be explicit about "those two great circles" (the orbit great circle and the longitude line of the point?)
• Section 8.4, first sentence, please add "of the swath" after "edge"
• Section 8.4, last sentence before Fig. 2 - does it mean to say "database table that contains the sensor (rather than orbit) information"?
• Section 8.8, last sentence, "during" should be deleted?
• Section 10 and 16.1 - add "for earth rotation" to end of section title
• Section 12.1, sentence 3, beginning "Technically" - not where the data are (which are on disk or tape somewhere), but where the sensor field of view is.
• Section 12.3, paragraph 2, line 2 - "an descending" should be "a descending". Both "it's" should be "its".
• Section 12.4, last sentence - change "are include" to "are included". Change "each granules" to "each granule".
• The word "granule" is used in several places, but is never defined.
• Section 12.5:
  • third sentence - insert "spatial" between "database" and "query".
  • paragraph 2, line 3 - change "desire accuracy" to "desired accuracy"
  • paragraph 3, line 4 - change "is" to "are"
• Section 13 - please change this section heading to "Informative References"