From 4b3e779f56b5fb75f548d28982b22403ac9135c3 Mon Sep 17 00:00:00 2001
From: claresinger <clareees@gmail.com>
Date: Fri, 3 Jun 2022 14:28:19 -0700
Subject: [PATCH] remove lon_perihelion parameter and update epoch to be given
 as a string that can be parsed as DateTime.

---
 docs/src/API.md                 |  1 -
 src/Planet/Planet.jl            |  8 +-------
 src/Planet/planet_parameters.jl |  3 +--
 src/parameters.toml             | 12 +++---------
 4 files changed, 5 insertions(+), 19 deletions(-)

diff --git a/docs/src/API.md b/docs/src/API.md
index 6a964b29..790e895a 100644
--- a/docs/src/API.md
+++ b/docs/src/API.md
@@ -102,7 +102,6 @@ Planet.mean_anom_epoch
 Planet.obliq_epoch
 Planet.lon_perihelion_epoch
 Planet.eccentricity_epoch
-Planet.lon_perihelion
 Planet.MSLP
 Planet.T_surf_ref
 Planet.T_min_ref
diff --git a/src/Planet/Planet.jl b/src/Planet/Planet.jl
index 0e193161..f6f8ccc4 100644
--- a/src/Planet/Planet.jl
+++ b/src/Planet/Planet.jl
@@ -52,7 +52,6 @@ export molmass_dryair,
     obliq_epoch,
     lon_perihelion_epoch,
     eccentricity_epoch,
-    lon_perihelion,
     MSLP,
     T_surf_ref,
     T_min_ref
@@ -157,7 +156,7 @@ function year_anom end
 function orbit_semimaj end
 """ Total solar irradiance (W/m``^2``) """
 function tot_solar_irrad end
-""" Time of  epoch (J2000) (s) """
+""" Time of  epoch """
 function epoch end
 """ Mean anomaly at the epoch (radians) """
 function mean_anom_epoch end
@@ -169,11 +168,6 @@ subtended at the Sun by the orbital arc from vernal equinox to perihelion). """
 function lon_perihelion_epoch end
 """ Orbital eccentricity at the epoch """
 function eccentricity_epoch end
-""" Longitude of perihelion (radians), measured relative to vernal equinox.
-The calculation of the mean anomaly is formulated such that the vernal equinox
-is fixed in the calendar. However, this requires tracking both the current longitude of perihelion
-as well as the reference longitude of perihelion at the reference time (epoch). """
-function lon_perihelion end
 """ Mean sea level pressure (Pa) """
 function MSLP end
 """ Mean surface temperature (K) in reference state """
diff --git a/src/Planet/planet_parameters.jl b/src/Planet/planet_parameters.jl
index 9cd0afc7..b09fe908 100644
--- a/src/Planet/planet_parameters.jl
+++ b/src/Planet/planet_parameters.jl
@@ -55,12 +55,11 @@ Planet.grav(ps::AbstractEarthParameterSet) = 9.81
 Planet.year_anom(ps::AbstractEarthParameterSet) = 365.26 * Planet.day(ps)
 Planet.orbit_semimaj(ps::AbstractEarthParameterSet) = 1 * astro_unit()
 Planet.tot_solar_irrad(ps::AbstractEarthParameterSet) = 1362.0
-Planet.epoch(ps::AbstractEarthParameterSet) = 2451545.0 * Planet.day(ps)
+Planet.epoch(ps::AbstractEarthParameterSet) = "2000-01-01T11:58:56.816"
 Planet.mean_anom_epoch(ps::AbstractEarthParameterSet) = deg2rad(357.52911)
 Planet.obliq_epoch(ps::AbstractEarthParameterSet) = deg2rad(23.432777778)
 Planet.lon_perihelion_epoch(ps::AbstractEarthParameterSet) = deg2rad(282.937348)
 Planet.eccentricity_epoch(ps::AbstractEarthParameterSet) = 0.016708634
-Planet.lon_perihelion(ps::AbstractEarthParameterSet) = deg2rad(282.937348)
 Planet.MSLP(ps::AbstractEarthParameterSet) = 1.01325e5
 Planet.T_surf_ref(ps::AbstractEarthParameterSet) = 290.0
 Planet.T_min_ref(ps::AbstractEarthParameterSet) = 220.0
diff --git a/src/parameters.toml b/src/parameters.toml
index e8a31f42..8763b157 100644
--- a/src/parameters.toml
+++ b/src/parameters.toml
@@ -511,9 +511,9 @@ type = "float"
 
 [epoch_time]
 alias = "epoch"
-value = 211813488000
-type = "float"
-description = "derived: 2451545.0 * [day]"
+value = "2000-01-01T11:58:56.816"
+type = "String"
+description = "J2000 epoch (Jan 1, 2000 11:58:56.816 UTC) as string"
 
 [mean_anomalistic_at_epoch]
 alias = "mean_anom_epoch"
@@ -538,12 +538,6 @@ alias = "eccentricity_epoch"
 value = 0.016708634
 type = "float"
 
-[longitude_perihelion]
-alias = "lon_perihelion"
-value = 4.938188299449
-type = "float"
-description = "(282.937348 degrees) in radians"
-
 [mean_sea_level_pressure]
 alias = "MSLP"
 value = 101325