Download or view GaiaTestGalactic.frink in plain text format
/* This program demonstrates graphing star positions with the Gaia satellite
data, specifically the data release 2 data. This is different than
GaiaTest.frink in that it remaps the stars to "galactic" coordinates.
It requires downloading the Gaia data (which is huge if you download it
all; the whole database is about 550 GB, and those are mostly gzipped
files!) from:
http://cdn.gea.esac.esa.int/Gaia/gdr2/
This program just uses the limited data set in gaia_source_with_rv which
contains data for about 7.2 million stars. The full data set contains about
1.2 billion stars.
The data for gaia_source_with_rv can be downloaded directly from
http://cdn.gea.esac.esa.int/Gaia/gdr2/gaia_source_with_rv/csv/
which is about 3.1 GB (gzipped!) of data; it's about 7.5 GB uncompressed.
The new gunzip function in Frink will allow you to process gzip-compressed
files in place.
Description of the whole data release is available at:
http://gea.esac.esa.int/archive/documentation/GDR2/
More specifically, the description of the gaia_source table used in this
program is available in section 14.1.1 of that document at:
http://gea.esac.esa.int/archive/documentation/GDR2/Gaia_archive/chap_datamodel/sec_dm_main_tables/ssec_dm_gaia_source.html
This attempts to plot semi-realistic colors for the stars. Dimmer stars
only have data in the green channel, so they are plotted as gray. The
sensors have a bias toward the green, as can be seen in the chart here:
https://www.cosmos.esa.int/web/gaia/iow_20180316
A reference image is available at:
https://www.cosmos.esa.int/web/gaia/gaiadr2_gaiaskyincolour
*/
use sun.frink
// Modify this path to where your Gaia files reside
dir = "/home/eliasen/builds/Gaia/gdr2/gaia_source_with_rv/csv"
g = new graphics
g.backgroundColor[0,0,0]
neutral = new color[1,1,1,.5]
for url = select[fileURLs[dir], %r/\.csv\.gz/]
{
println[url]
lineNum = 0
for line = lines[gunzip[url]]
{
if lineNum == 0
[colToName, nameToCol] = makeColumnDictionaries[line]
else
{
fields = split[",", line]
ra = eval[fields@5] degrees
decl = eval[fields@7] degrees
// TODO: Precess the coordinates to B1950.0 epoch
// using the apparentPosition function. Also parse
// and handle proper motion columns.
[l,b] = raDeclToGalactic[ra, decl]
l = (l + 1/2 circle) mod circle
redFlux = fields@57 // phot_rp_mean_flux
greenFlux = fields@47 // phot_g_mean_flux
blueFlux = fields@52 // phot_bp_mean_flux
if redFlux == "" or greenFlux == "" or blueFlux == ""
g.color[neutral]
else
{
redFlux = eval[redFlux] * 1.3
greenFlux = eval[greenFlux]
blueFlux = eval[blueFlux] * 1.3
sum = redFlux + greenFlux + blueFlux
red = redFlux / sum
green = greenFlux / sum
blue = blueFlux / sum
//println[type[redFlux] + "$redFlux $greenFlux $blueFlux"]
g.color[red, green, blue, .5]
}
g.fillRectCenter[-l, -b, .075 degree, .075 degree]
}
lineNum = lineNum + 1
}
}
println["Done reading. About to render graphics to screen."]
g.show[]
println["Done showing."]
println["Rendering graphics."]
g.write["GaiaTestGalactic.jpg", 3840, undef]
println["Done rendering."]
println["Inverting grays."]
g2 = g.invertGrays[]
println["Done inverting grays. Beginning printing"]
g2.print[]
println["Done printing."]
/** Makes two dictionaries that map column numbers to column
names and vice versa.
Returns:
[colToName, nameToCol]
*/
makeColumnDictionaries[line, print=false] :=
{
fields = split[%r/,/, line]
colToName = new dict
for i = rangeOf[fields]
colToName@i = fields@i
nameToCol = colToName.invert[]
if print
{
for key = sort[keys[colToName]]
println["$key\t" + colToName@key]
println[]
println[]
for key = lexicalSort[keys[nameToCol]]
println[nameToCol@key + "\t$key"]
}
return[colToName, nameToCol]
}
Download or view GaiaTestGalactic.frink in plain text format
This is a program written in the programming language Frink.
For more information, view the Frink
Documentation or see More Sample Frink Programs.
Alan Eliasen, eliasen@mindspring.com