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Interfaces, types, and functions for space science packages

License: Mozilla Public License 2.0

Julia 100.00%

astronomy astrophysics julia

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prakharcode xuanxu ravising-h matzipan patricknharris stjordanis

astrobase.jl's Issues

Convert between HJD <-> BJD?

Hi,

Awesome package, thanks for all of your work! I am slowly migrating some routines in Python over to Julia and was wondering if there was already a way to convert between HJD <-> BJD, similarly to the astropy snippet I found here? https://gist.github.com/StuartLittlefair/4ab7bb8cf21862e250be8cb25f72bb7a

from astropy.coordinates import SkyCoord, EarthLocation
from astropy import units as u
from astropy.time import Time

def helio_to_bary(coords, hjd, obs_name):
    helio = Time(hjd, scale='utc', format='jd')
    obs = EarthLocation.of_site(obs_name)
    star = SkyCoord(coords, unit=(u.hour, u.deg)) 
    ltt = helio.light_travel_time(star, 'heliocentric', location=obs)
    guess = helio - ltt
    # if we assume guess is correct - how far is heliocentric time away from true value?
    delta = (guess + guess.light_travel_time(star, 'heliocentric', obs)).jd  - helio.jd
    # apply this correction
    guess -= delta * u.d

    ltt = guess.light_travel_time(star, 'barycentric', obs)
    return guess.tdb + ltt

def bary_to_helio(coords, bjd, obs_name):
    bary = Time(bjd, scale='tdb', format='jd')
    obs = EarthLocation.of_site(obs_name)
    star = SkyCoord(coords, unit=(u.hour, u.deg))
    ltt = bary.light_travel_time(star, 'barycentric', location=obs) 
    guess = bary - ltt
    delta = (guess + guess.light_travel_time(star, 'barycentric', obs)).jd  - bary.jd
    guess -= delta * u.d
    
    ltt = guess.light_travel_time(star, 'heliocentric', obs)
    return guess.utc + ltt

which for example would return something like this:

> helio_to_bary("1:12:43.2 +31:12:43", 2457681.00027, "CTIO")
<Time object: scale='tdb' format='jd' value=2457681.0010844585>

Sorry if this is the wrong place to ask this!

The Plan

CC: @giordano

Comment and edit away 👍

Using Unitful.jl & UnitfulAstro.jl for unit handling

AstroBase currently uses its own unit types, and is limited to the set of units it implements. Is integrating Unitful and UnitfulAstro a desired feature? If so, I'd be interested in implementing this. But I wanted to check to see if that was a desired feature for AstroBase first.

Move to Julia 0.7

@prakharcode I would like to move to Julia 0.7 as soon as possible. Would that impede your work?

Julia Astro tutorials

[Didn't know where else to create this issue]
I recently came across the astropy tutorials website.
Can we implement a similar thing in julia ?
With the language getting better and stable and an exponentially increasing user base it'd be nice to have a bunch of tutorials covering the basic aspects of the package, examples, devs' guide etc.
@nolta @giordano @timholy @kbarbary @helgee

Roadmap to release

@giordano It seems that the LTS was bumped to 1.6. So the initial release should probably support 1.0. Don't you think?

Port useful ERFA functions

A

B

bi00 -> EarthAttitude
bp00 -> EarthAttitude
bp06 -> EarthAttitude
bpn2xy -> EarthAttitude

C

D

E

F

G

H

h2fk5 -> Astrometry
hfk5z -> Astrometry

I

icrs2g -> Astrometry
ir -> unneeded

J

jd2cal -> AstroTime
jdcalf -> AstroTime

L

N

O

obl06 -> EarthAttitude
obl80 -> EarthAttitude

P

R

S

T

U

X

xy06 -> EarthAttitude
xys00a -> EarthAttitude
xys00b -> EarthAttitude
xys06a -> EarthAttitude

Z

zp -> unneeded
~~zpv~~ -> unneeded
zr -> unneeded

Observatories

I’m curious about moving the common observatory information into this repo from AstroLib. In addition, would it be crazy to try adding an “Instrument” abstract type with some common methods values like what observatory, aperture, resolution, fwhm, or similar properties? An example usage would be broadening synthetic spectra dependent on what instrument the data is from (via FWHM lookup).

Relicense under MPLv2

AstroBase.jl, as is, already contains quite a few "derivative works", i.e. ports of BSD-licensed code, while AstroBase itself is MIT-licensed. That does not work because MIT is more permissive than BSD (see here). While the jury is still out on whether a port is actually a derivative work, I would much rather err on the side of caution and become compliant!

Since I expect the influx of more ports with various licenses, I would choose a license which is compatible with most others (excluding GPL of course 🤷‍♂). The Mozilla Public License v2 (MPLv2) fulfills these requirements: https://choosealicense.com/licenses/mpl-2.0/

Dear contributors,

Could you please indicate by commenting here whether you agree to a license change to MPLv2?

Cheers,
Helge

Contributors

@prakharcode has agreed
@matzipan has agreed
@timholy has agreed

Add benchmarks for all functions ported from ERFA

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