Due to user request, the number of output digits for Horizons observer table
ephemeris quantities #14 and #15 (sub-observer and sub-solar longitude and
latitude) will be increased 4 decimal places each.
This is expected to go live on 2020-Feb-12 (Wednesday) and could be relevant
to users expecting fixed-format column-based data positions (or lengths) for
those two quantities.
Reason for change:
The current 2 decimal place output can lead to rasterization and
discontinuities in derived functions and plots based on the output.
Increasing output to 6 decimals permits numerically smooth results,
though the additional digits are often not physically meaningful due to
most bodies having fairly low precision IAU rotation models (especially
the natrural satellites).
In addition, the header labels were obscure.
Details are given below.
-------------------------------------------------------------------------------
Jon Giorgini | Navigation & Mission Design Section
Senior Analyst | Solar System Dynamics Group
Jon.D.Giorgini@jpl.nasa.gov | Jet Propulsion Laboratory
-------------------------------------------------------------------------------
Quantity #14 (sub-observer latitude and longitude)
============
* CURRENT headers (space and comma-delimited options):
Case #1: NON-EARTH/MOON TARGET (IAU rotation model, 2 decimal places)
SPACE: Ob-lon Ob-lat
CSV : Ob-lon, Ob-lat,
Example of current output:
SPACE: Ob-lon Ob-lat
128.12 -17.12
CSV : Ob-lon, Ob-lat,
128.12, -17.12,
Case #2: EARTH/MOON TARGET (high-precision rot. model, 4 decimal places)
SPACE: Obsrv-lon Obsrv-lat
CSV : Obsrv-lon, Obsrv-lat,
Example of current output for Earth or Moon targets:
SPACE: Obsrv-lon Obsrv-lat
128.12345 -17.12345
CSV : Obsrv-lon, Obsrv-lat,
128.12345, -17.12345,
* FUTURE headers (space and coma-delimited options):
ALL rotatioal model cases
SPACE: ObsSub-LON ObsSub-LAT
CSV : ObsSub-LON, ObsSub-LAT,
Example of future output:
SPACE: ObsSub-LON ObsSub-LAT
128.123456 -17.123456
CSV : ObsSub-LON, ObsSub-LAT,
128.123456, -17.123456,
Quantity #15 (sub-solar longitude and latitude)
============
* CURRENT headers (space and comma-delimited options):
Case #1: NON-EARTH TARGET (IAU rotation model, 2 decimal places)
SPACE: Sl-lon Sl-lat
CSV : Sl-lon, Sl-lat,
Example of current output:
SPACE: Sl-lon Sl-lat
128.12 -17.12
CSV : Sl-lon, Sl-lat,
128.12, -17.12,
Case #2: EARTH TARGET (high-precision rot. model, 4 decimal places)
SPACE: Solar-lon Solar-lat
CSV : Solar-lon, Solar-lat,
Example of current output:
SPACE: Solar-lon Solar-lat
128.12345 -17.12345
CSV : Solar-lon, Solar-lat,
128.12345, -17.12345,
* FUTURE headers (space and coma-delimited options):
ALL rotatioal model cases
SPACE: SunSub-LON SunSub-LAT
CSV : SunSub-LON, SunSub-LAT,
Example of future output:
SPACE: SunSub-LON SunSub-LAT
128.123456 -17.123456
CSV : SunSub-LON, SunSub-LAT,
128.123456, -17.123456,
