1. Gaia Tomaž Zwitter Gaia: > 1.1 billion objects (V ≤ 20.9),
positions accurate to between 5 and 400 μas,
spatial resolution ~ 100 mas,
blue and red SED at epochs over 5-9 years,
RVs for objects brighter than V~15.5, spectroscopic parameters for the one brighter than V~12.5.

2. Gaia - first data release
The first data release (September 2016): (Brown et al. 2016)
positions, parallaxes (error ~0.3 mas) and proper motions (error ~1 mas/yr) for 2 million Hipparcos/Tycho-2 stars;
positions (error ~10 mas) and G magnitudes (error < 0.03 mag) for 1.1 billion objects (V ≤ 20.9); (V = 1.02 G − 0.24 for V-I ~ 0.7)
G-band light curves and characterization for ~3000 Cepheids and RR Lyrae stars around the south ecliptic pole.
QSOs: (Lindegren et al. 2016, Mignard et al. 2016)
135,000 observed (from the list of Andrei et al. 2014);
positions compared to VLBI reference frame;
formal standard error for 2191 quasars (with 17.6 < V < 20.7) compared to ICRF2: 0.76 mas for 50% and 3.35 mas for 90% sources;
alignement with the ICRF2 to better than 0.1 mas at epoch , non-rotation to within 0.03 mas/yr;
there are now 11,444 objects with VLBI positions, i.e. 3.5-times more than in ICRF2 (Petrov & Kovalev 2016).

3. Sky chart of 1,142,679,969 sources
Brown et al. 2016

4. 3 problems:
damped throughput (ice),
basic angle variation,
stray-light.
They are now solved or
under control.

5. Focal plane: 3 main instruments
Prusti et al. 2016

6. Positional accuracy errors after 5 yr mission Jester et al. 2005
Proft et al. 2016
Brown et al. 2016

7. Gaia: photometric accuracy
3 bands: white (G: nm), blue (BP: nm), red (RP: nm),
~ 72 transits in 5 yrs (min 50, max 200+).
errors for a single transit

8. Gaia QSOs: λ coverage by BP and RP spectra
Proft et al. 2016, number of photons per 5 transits

9. Redshifts of QSOs with V ~ 20.2 after 5 yrs of mission
Proft et al. 2016

10. Gaia QSOs: variability detection by sums of five transits
z = 2.03
r' = 17.5
(Proft et al. 2016)

11. Offsets in Gaia vs. VLBI positions
Kovalev et al. (2017) determined VLBI-jet direction for AGNs observed by Gaia.
Position offsets along the jet require strong, extended parsec- scale optical jets.
Small (<1 mas) offsets in direction opposite to the jet can be due to extended VLBI jet structure or a “core-shift” effect due to synchrothon opacity.

12. Gaia timeline Launch: 19 December 2013,
The 1st data release: 14 September 2016:
TGAS parallaxes & proper motions for Tycho stars, VLBI coordinate system match.
The 2nd data release: April 2018:
Five-parameter astrometric solutions for all sources with acceptable formal standard errors (>109 anticipated), and positions (α, δ) for sources for which parallaxes and proper motions cannot be derived.
G and integrated GBP and GRP photometric fluxes and magnitudes for all sources.
Median radial velocities for sources brighter than GRVS= 12 mag (V=12.8 for G0 V star, V=13.2 for K1 III star).
For stars brighter than G = 17 mag estimates of the effective temperature and, where possible, line-of-sight extinction will be provided, based on the above photometric data.
Photometric data for a sample of variable stars.
Epoch astrometry for a pre-selected list of >10,000 asteroids.
Mission duration: 2019, 2021, 2023? Final release with everything: 3 yrs later.

13. Gaia timeline In perspective (7 months from now):
Parallax & proper motion accuracy of 70 μas implies 10% error at 1.3 kpc and 3% error at 400 pc.
BP/RP: only integrated magnitudes, perhaps to be so at least to 2020 or
Parameters: Teff+reddening from BP/RP, logg from G & parallax.
RVS: for V < 12, maybe V < 13, only average reported and for non-variable RVs, accuracy ~1-2 km/s.
So ground based surveys valuable for: RVs, spectroscopic params, abundances.
Why we need accurate RVs? Long period SB1s, vertically resolved atmospheres,
cluster micro-dynamics, LSR.

14. On-going ground-based optical stellar spectroscopic surveys
Goals:
individual element abundances, radial velocities.
Surveys:
RAVE (
LAMOST (
Gaia-ESO (
Galah (
Apogee,
FunnelWeb.

15. The 3 ground-based surveys

16. ... it was:

17. ... it is:
(a bug in astro-py discovered)

20. shift applied: RVRAVE = RVGalah – 0.17 ± 0.03 km/s.

23. shift applied: RVHR21 = RVHR15N + 0.70 ± 0.05 km/s.

24. RV shifts between surveys
RAVE = Galah – 0.17 ± 0.03 km/s
HR15N = HR10 = Galah ± 0.06 km/s
UVESU = Galah ± 0.05 km/s
UVESL = HR21 = Galah ± 0.03 km/s
Note how small are the errors.
Next: stellar parameters

25. Fe abundance of Galah and RAVE

26. + median, within □ 68% of objects.