master_bash.sh

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# Master bash file - will run on interval specified by crontab
# Initiates scrape & sgp4 computations for all spacecraft

# Prep
# Run as root: chown -R <user> /usr/share/celestia/extras
# Run as root: chown -R <user> /usr/share/celestia/extras-standard
# Add .bak extension to original SSC files or remove

# User Inputs
# Web addresses for Python curl
# Pertinent lines for parsing
# Folder structures

# Outputs
# Updated LOG file for each spacecraft
# New TLE file for each spacecraft
# XYZV files for each spacecraft

# Goals
# Add future expansion to scrape from multiple web pages

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# Change from ~/ (crontab default) to working directory and create LOG & TLE
cd /home/<user>/<...>
mkdir -p ./LOG
mkdir -p ./TLE
cd ./TLE

# Move custom python scripts into python-sgp4 submodule
mv date.py ./python-sgp4/date.py
mv sgp4.py ./python-sgp4/sgp4.py


############
## scrape ##
############

# Initialization variables
pages=(stations tdrss gps-ops)    # stations, tdrss, gps-ops, sarsat, tle-new, visual, geo
toi=(ISS HST GPS)   # spacecraft of interest - string base

for p in ${pages[@]};

    do
    # Download TLE txt data from the web, get its date, and setup folder structure for ssc and xyzv files
    dl=`curl -i http://www.celestrak.com/NORAD/elements/$p.txt`
    date=`echo "$dl" | awk "NR==4" | tail -c +16 | head -c -2`
    dir=/usr/share/celestia/extras/$p
    mkdir $dir
    mkdir $dir/data

    # Set pre-loop variables
    pos=11  # last line of curl -i is line 10
    end=`echo "$dl" | wc -l`    # end is last line number

    # Main loop
    while [ $pos -lt $end ]

        do
        # Set name of spacecraft
        name=`echo "$dl" | awk "NR==$pos" | tr -s " " "_" | head -c -3` # trims carriage return "\r" and last "_"
        
        # Check against toi array - improve
        for n in "${toi[@]}"; do if [[ $name == $n* ]]; then

        # Create TLE file from selected data
        echo "$dl" | awk "NR==$pos+1,NR==$pos+2" > ./_$name
        
        # If TLE file does not exist, create and prep a new log file
        if [ ! -e "./$name" ]
            then echo -e "# Running log file for $name TLE data from Celestrack TLE repository (sourced from NORAD)\n\n# Line 1 is: <line> <sat_num> <int_desig> <ep_yr_fracday> <1_der_mm> <2_der_mm> <drag> <eph_typ> <el_set> <cs>\n# TLE Line 2 is: <line> <sat_num> <incl> <ra> <ecc> <peri> <m_anom> <m_mot> <rev_num> <cs>\n" > ../LOG/$name.txt
        fi

        # Compare to last TLE file
        if ! diff -q ./_$name ./$name
            then
                # Remove original TLE file and rename temp to new
                rm ./$name
                mv ./_$name ./$name
        
                # Write updated data to log (in LOG folder) - combine?
                echo "#####################################################################" >> ../LOG/$name.txt
                echo "$date" >> ../LOG/$name.txt
                echo "$dl" | awk "NR==$pos+1,NR==$pos+2" >> ../LOG/$name.txt
                echo >> ../LOG/$name.txt


                ############
                ##  sgp4  ##
                ############        
        
                # Run calculations based on new TLE data - pass variables to Python
                s_date=`python ../python-sgp4/date.py $name`
                #s_date=`TZ=UTC date +"%a, %d %b %Y %H:%M:%S GMT"`
                #es=`date +"%s" -d "$s_date"`  # epoch seconds
                ss=600   # step size in seconds
                ts=36   # time span in hours
                e_date=`TZ=UTC date +"%a, %d %b %Y %H:%M:%S GMT" -d "$s_date $ts hours"` # not passed to Python, used to setup xyzv file
            
                echo -e "# Celestia xyzv file generated by sgp4.py\n\n# Satellites deviate from the ideal orbits described in TLE files by 1-3 km/day\n\n# Data post date:       $date\n# Calc start date:      $s_date\n# Calc end date:        $e_date\n# Time span (hours):    $ts\n# Step size (sec):      $ss\n\n# Records are <jd> <x> <y> <z> <vel x> <vel y> <vel z>\n#   Time is a TDB Julian date\n#   Position in km\n#   Velocity in km/sec\n\n######################################################\n" > $dir/data/$name.xyzv
            
                ### Run sgp4.py script ###
                # variables with spaces should be in double quotes
                python ../python-sgp4/sgp4.py $name $ts $ss >> $dir/data/$name.xyzv # passes <1 filename> <2 current date> <3 current epoch> <4 time span> <5 step size> from bash to Python
            
                # Create SSC file
                echo -e ""\""$name"\"" "\""Sol/Earth"\""\n{\nClass "\""spacecraft"\""\n#Mesh "\""<file>"\""\nRadius 0.01\nAlbedo 0.7\nSampledOrbit "\""$name.xyzv"\""\n\nBodyFrame {\n    TwoVector {\n        Center "\""Sol/Earth/$name"\""\n        Primary {\n            Axis "\""z"\""\n            RelativePosition { Target "\""Sol/Earth"\"" }\n        }\n        Secondary {\n            Axis "\""x"\""\n            RelativeVelocity { Target "\""Sol/Earth"\"" }\n        }\n    }\n}\n\n}" > $dir/$name.ssc
            
            else
                # Remove temp TLE file
                rm ./_$name
        fi
        
        # Check against toi array - improve
        fi; done
        
        # Increment pos variable by 3 (lines per spacecraft)
        let pos+=3

    done

done