progress on sunlight article

_posts/2021-04-14-iss-eclipse-determination/iss-eclipse-determination.Rmd

@@ -1,24 +1,115 @@
 ---
 title: "ISS Eclipse Determination"
 description: |
-  Determining how much sunlight a body 
-draft: true
+  Determining how much sunlight a body is receiving.
+draft: false
 author:
   - name: Anson Biggs
     url: https://ansonbiggs.com
-date: 04-14-2021
+repository_url: https://gitlab.com/lander-team/air-prop-simulation
+date: 04-01-2021
+fig_width: 6
+fig_align: "center"
 output:
   distill::distill_article:
     self_contained: false
+categories:
+  - Julia
+  - Astrodynamics
+#bibliography: ../../citations.bib
+creative_commons: CC BY
+preview: preview.png
 ---
 
+Determining the eclipses a satellite will encounter is a major driving factor when designing a mission in space. Thermal and power budgets have to be made with the fact that a satellite will periodically be in the complete darkness of space with no solar radiation to power the solar panels and keep the spacecraft from freezing. 
 
 ```{r setup, include=FALSE}
-knitr::opts_chunk$set(echo = FALSE)
+knitr::opts_chunk$set(echo = TRUE, results = 'hide')
+library(JuliaCall)
+#julia_setup(JULIA_HOME = "/opt/julia-1.6.1/bin/")
+julia_setup(installJulia = TRUE)
 ```
 
-Distill is a publication format for scientific and technical writing, native to the web.
+## What is an Eclipse
 
-Learn more about using Distill at <https://rstudio.github.io/distill>.
+![Geometry of an Eclipse](geometry.svg)
 
 
+![Body Radius's and Position Vectors](vectors_radiuss.svg)
+
+
+## The Code
+
+```{julia, code_folding=TRUE}
+using Unitful
+using LinearAlgebra
+using SatelliteToolbox
+using Plots
+using Colors
+theme(:ggplot2)
+```
+
+
+```{julia}
+ISS = tle"""
+ISS (ZARYA)
+1 25544U 98067A   21103.84943184  .00000176  00000-0  11381-4 0  9990
+2 25544  51.6434 300.9481 0002858 223.8443 263.8789 15.48881793278621
+"""
+```
+
+```{julia}
+orbit = init_orbit_propagator(Val(:twobody), ISS[1]);
+time = 0:0.1:((24 / ISS[1].n) .* 60 * 60);
+o, r, v = propagate!(orbit, time);
+```
+
+
+```{julia}
+function sunlight(Rbody, r_sun_body, r_body_sc)
+    Rsun = 695_700u"km"
+    
+    hu = Rbody * norm(r_sun_body) / (Rsun - Rbody)
+    
+    θe = acos((r_sun_body ⋅ r_body_sc) / (norm(r_sun_body) * norm(r_body_sc)))
+
+    θu = atan(Rbody / hu)
+    du = hu * sin(θu) / sin(θe + θu)
+
+    θp = π - atan(norm(r_sun_body) / (Rsun + Rbody))
+    dp = Rbody * sin(θp) / cos(θe - θp)
+
+    S = 1
+    if (θe < π / 2) && (norm(r_body_sc) < du)
+        S = 0
+    end
+    if (θe < π / 2) && ((du < norm(r_body_sc)) && (norm(r_body_sc) < dp))
+        S = (norm(r_body_sc .|> u"km") - du) / (dp - du) |> ustrip
+    end
+
+    return S
+end
+```
+
+```{julia}
+S = r .|> R -> sunlight(6371u"km", [0.5370, 1.2606, 0.5466] .* 1e8u"km", R .* u"m")
+```
+
+## Plotting the Results
+
+```{julia, code_folding=TRUE, results='show',layout="l-body-outset",fig.cap= "Rocket Motor Data: [@thrustcurve]", preview=TRUE }
+light_range = range(colorant"black", stop = colorant"yellow", length = 101);
+light_colors = [light_range[unique(round(Int, 1 + s * 100))][1] for s in S];
+
+plot(
+    LinRange(0, 24, length(S)),
+    S .* 100,
+    linewidth = 5,
+    legend = false,
+    color = light_colors,
+);
+
+xlabel!("Time (hr)");
+ylabel!("Sunlight (%)");
+title!("ISS Sunlight Over a Day")
+```