<p>What size of the grating on GAIA RVS spectroscope ?</p>

<h2>How many lines on mm, or what defraction angle for 850 nm wavelenth light ?</h2>

<p>I find some more details here: <a href="http://sci.esa.int/gaia/44092-gaia-rvs-grating/" rel="nofollow noreferrer">http://sci.esa.int/gaia/44092-gaia-rvs-grating/</a> and <a href="http://sci.esa.int/gaia/44093-state-of-the-art-grating-for-gaia/" rel="nofollow noreferrer">http://sci.esa.int/gaia/44093-state-of-the-art-grating-for-gaia/</a>
The GAIA RVS grating has dimensions of 20.5 cm × 15.5 cm and 302.11 grooves per mm.</p>

CC BY-SA 3.0
2018-01-02T12:54:51.543Z
For RVS, Gaia uses two prisms, a blue and red one. That's a good thing to google.
AtmosphericPrisonEscape
CC BY-SA 3.0
2018-01-04T05:29:36.123Z
You are wrong. Prisms uses in the photometric instrument - spectrometer of low resolution. RVS (radial velocity spectrometer) use the grating, see http://sci.esa.int/gaia/40129-payload-module/?fbodylongid=1916
tsikraserg
CC BY-SA 3.0
2018-01-04T05:40:08.297Z
Also see the question on this sight - Why does Gaia use only calcium NIR lines for stellar radial velocity measurements? - https://astronomy.stackexchange.com/questions/18374/why-does-gaia-use-only-calcium-nir-lines-for-stellar-radial-velocity-measurement
tsikraserg
CC BY-SA 3.0
2018-01-04T16:42:00.870Z
Ah you're right, I confused those two parts. The calcium triplet is simply very well detectable in most stars, just as the document you've linked also states.
AtmosphericPrisonEscape
<gaia>
What a grating on GAIA RVS spectroscope?
tsikraserg
# What a grating on GAIA RVS spectroscope?

(Asked by: username_0 on 2018-01-02)

What size of the grating on GAIA RVS spectroscope ?

## How many lines on mm, or what defraction angle for 850 nm wavelenth light ?

I find some more details here: <http://sci.esa.int/gaia/44092-gaia-rvs-grating/> and <http://sci.esa.int/gaia/44093-state-of-the-art-grating-for-gaia/>
The GAIA RVS grating has dimensions of 20.5 cm × 15.5 cm and 302.11 grooves per mm.

**Tags:** gaia
> **Comments:**
> **username_1**: For RVS, Gaia uses two prisms, a blue and red one. That's a good thing to google.  
> **username_0**: You are wrong. Prisms uses in the photometric instrument - spectrometer of low resolution. RVS (radial velocity spectrometer) use the grating, see http://sci.esa.int/gaia/40129-payload-module/?fbodylongid=1916  
> **username_0**: Also see the question on this sight - Why does Gaia use only calcium NIR lines for stellar radial velocity measurements? - https://astronomy.stackexchange.com/questions/18374/why-does-gaia-use-only-calcium-nir-lines-for-stellar-radial-velocity-measurement  
> **username_1**: Ah you're right, I confused those two parts. The calcium triplet is simply very well detectable in most stars, just as the document you've linked also states.  

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