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. ASPSuite version 2017.2.77.0 and earlier only display (and allow browsing) to the ephemeris file. Version 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 one of the links 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 Julian Date or day of the year (e.g. 1-365).

Ephemeris files:

ftp://cddis.gsfc.nasa.gov/gnss/products/

ftp://igs.ensg.ign.fr/pub/igs/products/

Igu – Ultra-rapid Solution – GNSS orbit combination solutions (ultra-rapid solution) produced by the International GNSS Service (IGS). These sub-daily files of satellite ephemerides are useful for real-time and near real-time applications; the ultra-rapid solution includes both observed and predicted satellite orbits. The solutions are released four times per day, at 03:00, 09:00, 15:00, and 21:00 UTC. At the time of release, the observed orbits have an initial latency of 3 hours. More information on this product can be found at https://cddis.nasa.gov/Data_and_Derived_Products/GNSS/gnss_igsuorb.html

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.

WWWW/iguWWWWD_HH.sp3.Z

as described in the table below.

Code Meaning
WWWW GPS week
D day of week (0-6, 7 indicates weekly)
HH hour of day (00, 06, 12, 18)
.Z UNIX compressed file

Igr – Rapid Solution – GNSS orbit combination solutions (rapid solution) produced by the International GNSS Service (IGS). These daily files of satellite ephemerides contain 24 hours (from 00:00 to 23:45 UTC) and are provided in 15-minute intervals in SP3 format including accuracy codes. This rapid solution has a quality nearly comparable to that of the final IGS products. The solution consists of daily orbit and clock files, generated on a daily basis by rapid combining solutions from individual IGS Analysis Centers, released approximately 17 hours after the end of the UTC day. More information on this product can be found at https://cddis.nasa.gov/Data_and_Derived_Products/GNSS/gnss_igsrorb.html

WWWW/igrWWWWD.sp3.Z

as described in the table below.

Code Meaning
WWWW GPS week
D day of week (0-6, 7 indicates weekly)
.Z UNIX compressed file

Igs – Final Solution – Summary file produced by the International GNSS Service (IGS) with the GNSS orbit combination solutions (final solution). The summary file describes the combination process and provides statistics on the analysis. This final solution is the most consistent and highest quality IGS solutions, summarizing the analysis performed for the daily orbit and ERP combination solution, generated on a weekly basis approximately 13 days after the end of the solution week. More information on this product can be found at https://cddis.nasa.gov/Data_and_Derived_Products/GNSS/gnss_igssum.html

Igv – Mixed – Contains both GPS and GLONASS

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 using ASPSuite.

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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