Ephemeris and Navigation Data Files

During processing in ASPSuite, two files are obtained as part of the “Auto-download” step on the ephemeris tab: an ephemeris (sp3) file and a broadcast (brdc*.YYn) navigation file. ASP Suite versions 2017.2.77.0 and earlier only display (and allow browsing) to the ephemeris file. 2017.2.78.0 and later allow both files to be browsed or auto-downloaded.

If the navigation file isn’t specified or downloaded, ASPSuite uses the rover navigation file (e.g. 20180119192120.18P, created from the .sbf). If Loki was on for too short a time (typically less than 15-18 minutes) due to a short flight, you may fail to get a fixed trajectory solution. You may browse to the navigation file from your base station (either .18N or .18P files), or you may download a broadcast navigation file using one of the links below.

If the ephemeris file isn’t specified or downloaded, use the link below to obtain them. You’ll need to know the GPS week and day (0-6, where 0 is Sunday and 6 is Saturday) for ephemeris files. For navigation files, you’ll need to know the day of the year (e.g. 1-365).

 

Two links to ephemeris files:

GPS
ftp://cddis.gsfc.nasa.gov/gps/products/

GPS+GLONASS
ftp://igs.ensg.ign.fr/pub/igs/products/

First, pick the GPS week folder (e.g. 1984). Then find as many as 4 .sp3 files: igu<week#><day#>_00, or _06, or _012, or _018.sp3.Z. Always get the “highest one available for that day”. For Friday of week 1984, that is igu19845_18.sp3.Z. If that one isn’t available, next is igu19845_12.sp3.Z, and so on. Download and unzip, then browse to the file in ASP Suite.

Igu – Ultra rapid – Available immediately after the flight.

Igr – Rapid – Only available after 24 hours.

Igs- Final  – only available after 12-14 days.

Igv- Mixed – Contains both GPS and GLONASS

 

Two links to broadcast navigation files:
ftp://cddis.gsfc.nasa.gov/gnss/data/daily/
ftp://igs.ensg.ign.fr/pub/igs/data/

Select the year folder, then the day folder (Jan 19th is 019), then pick the 18n folder to find: brdc0190.18n.Z (note the extra ‘0’ at the end—that’s expected). Download, unzip, then browse to the file in the ASP Suite.

Other locations for ephemeris and broadcast navigation files may be found using this link:

https://kb.igs.org/hc/en-us/articles/202054393-IGS-FTP-Sites

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