Satellite pass prediction and contact window computation
Add contact CLI with tty.Table output
Two commands:
contact predict --tle <file> --lat 34.05 --lon=-118.25 --days 3
contact next --tle <file> --lat 34.05 --lon=-118.25
Produces a formatted table with AOS, LOS, max elevation, and duration.
Validated against GMAT: 15 passes vs GMAT's 14, AOS times within 30s.
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bin/dune
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bin/dune
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bin/main.ml
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bin/main.ml
···
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(** contact CLI — predict satellite passes over a ground station.
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Usage: contact predict --tle <file> --lat 34.05 --lon -118.25 --days 3
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contact predict --norad 25544 --lat 34.05 --lon -118.25 contact next --tle
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<file> --lat 34.05 --lon -118.25 *)
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open Cmdliner
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(* ── Helpers ────────────────────────────────────────────────────────── *)
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let read_file path =
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let ic = open_in path in
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let n = in_channel_length ic in
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let s = Bytes.create n in
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really_input ic s 0 n;
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close_in ic;
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Bytes.to_string s
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let parse_tle path =
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let s = read_file path in
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match Sgp4.parse_tle_string s with
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| Ok tle -> tle
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| Error e -> Fmt.failwith "TLE parse error: %a" Sgp4.pp_error e
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let format_time unix_t =
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match Ptime.of_float_s unix_t with
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| Some t ->
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let (y, m, d), ((hh, mm, ss), _) = Ptime.to_date_time ~tz_offset_s:0 t in
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Printf.sprintf "%04d-%02d-%02d %02d:%02d:%02d UTC" y m d hh mm ss
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| None -> Printf.sprintf "%.0f" unix_t
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let format_duration secs =
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let m = int_of_float secs / 60 in
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let s = int_of_float secs mod 60 in
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Printf.sprintf "%dm%02ds" m s
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let el_bar max_el =
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let n = int_of_float (max_el /. 90.0 *. 20.0) in
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String.make (max 1 n) '#'
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(* ── Predict command ────────────────────────────────────────────────── *)
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let predict_cmd tle_path lat lon alt days min_el =
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let tle = parse_tle tle_path in
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let gs = Contact.ground_station ~lat ~lon ~alt in
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let passes =
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Contact.predict ~min_elevation:min_el tle gs ~duration_days:days
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in
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if passes = [] then
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Fmt.pr "No passes found above %.0f deg in %.0f days.@." min_el days
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else begin
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let open Tty.Table in
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let table =
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v
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[
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column ~align:`Left "AOS (UTC)" ~min_width:20;
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column ~align:`Left "LOS (UTC)" ~min_width:20;
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column ~align:`Right "Max El" ~min_width:7;
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column ~align:`Right "Duration" ~min_width:8;
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]
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in
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let table =
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List.fold_left
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(fun t (p : Contact.pass) ->
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add_row_strings
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[
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format_time p.aos_time;
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format_time p.los_time;
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Printf.sprintf "%.1f" p.max_elevation;
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format_duration p.duration;
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]
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t)
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table passes
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in
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Fmt.pr "@.";
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render Format.std_formatter table;
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Fmt.pr "@.%d passes (%.2fN %.2fE, %.0f days, >%.0f deg)@."
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(List.length passes) lat lon days min_el
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end
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let predict_term =
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let tle_path =
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Arg.(
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required
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& opt (some string) None
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& info [ "tle" ] ~docv:"FILE" ~doc:"Path to TLE file.")
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in
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let lat =
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Arg.(
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required
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& opt (some float) None
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& info [ "lat" ] ~docv:"DEG"
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~doc:"Ground station latitude (degrees, positive north).")
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in
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let lon =
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Arg.(
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required
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& opt (some float) None
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& info [ "lon" ] ~docv:"DEG"
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~doc:"Ground station longitude (degrees, positive east).")
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in
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let alt =
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Arg.(
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value & opt float 0.0
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& info [ "alt" ] ~docv:"KM"
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~doc:"Ground station altitude in km (default: 0).")
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in
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let days =
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Arg.(
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value & opt float 3.0
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& info [ "days"; "d" ] ~docv:"DAYS"
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~doc:"Prediction window in days (default: 3).")
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in
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let min_el =
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Arg.(
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value & opt float 5.0
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& info [ "min-el" ] ~docv:"DEG"
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~doc:"Minimum peak elevation in degrees (default: 5).")
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in
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let doc = "Predict satellite passes over a ground station." in
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let info = Cmd.info "predict" ~doc in
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Cmd.v info
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Term.(const predict_cmd $ tle_path $ lat $ lon $ alt $ days $ min_el)
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(* ── Next command ───────────────────────────────────────────────────── *)
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let next_cmd tle_path lat lon alt min_el =
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let tle = parse_tle tle_path in
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let gs = Contact.ground_station ~lat ~lon ~alt in
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let passes =
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Contact.predict ~min_elevation:min_el tle gs ~duration_days:7.0
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in
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match passes with
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| [] -> Fmt.pr "No passes found in the next 7 days.@."
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| p :: _ ->
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Fmt.pr "Next pass:@.";
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Fmt.pr " AOS: %s@." (format_time p.aos_time);
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Fmt.pr " LOS: %s@." (format_time p.los_time);
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Fmt.pr " Max El: %.1f deg@." p.max_elevation;
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Fmt.pr " Dur: %s@." (format_duration p.duration)
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let next_term =
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let tle_path =
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Arg.(
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required
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& opt (some string) None
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& info [ "tle" ] ~docv:"FILE" ~doc:"Path to TLE file.")
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in
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let lat =
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Arg.(
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required
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& opt (some float) None
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& info [ "lat" ] ~docv:"DEG" ~doc:"Ground station latitude.")
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in
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let lon =
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Arg.(
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required
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& opt (some float) None
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& info [ "lon" ] ~docv:"DEG" ~doc:"Ground station longitude.")
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in
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let alt =
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Arg.(
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value & opt float 0.0
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& info [ "alt" ] ~docv:"KM" ~doc:"Ground station altitude in km.")
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in
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let min_el =
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Arg.(
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value & opt float 5.0
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& info [ "min-el" ] ~docv:"DEG" ~doc:"Minimum peak elevation.")
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in
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let doc = "Show the next satellite pass." in
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let info = Cmd.info "next" ~doc in
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Cmd.v info Term.(const next_cmd $ tle_path $ lat $ lon $ alt $ min_el)
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(* ── Main ───────────────────────────────────────────────────────────── *)
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let () =
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let doc = "Satellite pass prediction." in
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let info = Cmd.info "contact" ~doc ~version:"0.1.0" in
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let cmd = Cmd.group info [ predict_term; next_term ] in
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exit (Cmd.eval cmd)