IAU Working Group Densification of Optical Reference Frames
last update: 2009 May 08, Norbert Zacharias
3. Space-based astrometric projects
===================================
The positional accuracy is given for end of mission per coordinate.
If 2 numbers are given the smaller is for the best performance and
the larger for the positional accuracy at the limiting magnitude.
For all projects the performance for parallax and proper motions is
numerically about the same as for positional accuracy.
---------------------------------------------------------------------
project central epoch mission mag number positional band
name or expected duration range objects accuracy pass
launch date year mas nm
---------------------------------------------------------------------
Hipparcos 1991.25 3.7 -1..12 118 k 0.5 2.0 400- 600
---------------------------------------------------------------------
Nano-Jasmine 2010 2 z<= 8 100 k 3.0 600-1000
Small-Jasmine 2015 1.5 Kw<=12 30 k 0.01 .. 1500-2500
---------------------------------------------------------------------
J-MAPS 2012 3 1..12 10 m 1.0 700- 900
Gaia 2013 5 7..20 1000 m 0.01 0.3 330-1000
SIM-Lite 2018 5-10 0..20 20 k 0.001 400- 900
---------------------------------------------------------------------
Hipparcos is the only astrometric space mission successfully completed
as of today. The original catalog was published in 1997 [01], while
a complete re-reduction significantly improved astrometric results
for bright stars [02]. The star-mapper information of the Hipparcos
mission was used to produce the Tycho-2 star catalog [03] of the
2.5 million brightest stars in the sky. Tycho-2, with somewhat lower
accuracy (10 to 100 mas) than Hipparcos was and is the first step
of the much needed densification of the optical reference frame,
widely used as the reference catalog for almost all of the ground-
based astrometric projects and sky surveys listed above. Tycho-2
utilizes over 100 ground-based early epoch star catalogs, with the
AC (see above) being the most significant contribution, to derive
proper motions on the 2 mas/yr level. The impact of the Hipparcos
mission on astronomy has recently been reviewed [04].
Nano-Jasmine is a microsatellite (25 kg) developed at the Japanese Space
Agency [05]. The telescope has only 5 cm aperture and a 1k CCD will
be used in the near IR z band for an all-sky survey.
Small-Jasmine is a planned mission of the Japanese Space Agency [06].
It will operate in the near IR (k band) and observe about
10 million stars in the galactic bulge region in overlapping
fields. This is a scaled down version of a bigger spacecraft
(Jasmine) planned for the 2020s.
J-MAPS is the Joint Milli-Arcsecond Pathfinder Survey, a space astrometry
mission lead by the U.S. Navy. It will observe all sky with a single
aperture stare mode operation of overlapping fields [07]. Utilizing
different integration times and a CMOS-hybrid detector it will be able
to observe bright stars and also reach QSOs to link to the ICRF.
The numbers given in the table are for the core mission, many fainter
stars will likely be observed at somewhat lower accuracy.
Combining with Hipparcos, proper motions with an accuracy of about
0.1 mas/yr will be obtained for those stars [08].
Gaia is the next ESA astrometric flagship mission [09]. It is a large,
2-aperture, scanning satellite with an array of CCDs as detectors.
It will provide about 10 to 300 microarcsecond astrometry (depending
on magnitude) for a billion stars.
SIM-Lite, the Astrometric Observatory, is the NASA-JPL developed Space
Interferometry Mission [10,11]. All technical milestones and external
reviews have been passed with flying colors. SIM in one or another
incarnation was recommended by the past 2 Decadal Surveys and was
recently pushed behind JWST due to NASA budget problems. SIM can
achieve micro-arcsecond accuracy over the full magnitude range by
staring at selected targets. It is capable of detecting Earth-like
planets around nearby stars (in narrow angle mode, 1 microarcsecond) [12]
and can perform a host of other exciting astrophysics, mainly utilizing
its wide-angle mode (4 microarcsecond absolute astrometry). Establishing
a new celestial reference frame is part of the mission, as is a general
observer program beyond about a dozen key science programs.
[01] ESA, SP-1200, (1997) 17 volumes, also available from data centers
[02] van Leeuwen, F. (2007)
Hipparcos, the new reduction of the raw data,
Springer, Astroph. and Space Science Library series
[03] Perryman, M. (2009)
Astronomical Applications of Astrometry,
Cambridge Univ.Press
[04] Hog, E., Fabricius, C., Makarov, V.V. et al. (2000),
The Tycho-2 Catalogue of the 2.5 million brightest stars,
A&A 355, L27
[05] Gouda, N. et al. (2009),
Nano-Jasmine, IAU GA, Com.8 meeting
[06] Gouda, N., Kobayashi, Y., Yamada, Y., Yano, T. (2008)
in proceed. IAU Symp.248, p.316, Cambridge Univ.Press
Eds. W.Jin, I.Platais, M.A.C.Perryman
[07] Zacharias, N., Dorland, B. (2006),
Concept of a stare-mode astrometric mission,
PASP, 118, 1419
[08] Gaume,R., Dorland,B,. Hennessy,G., et al. (2009),
The Joint Milli-Arcsecond Pathfinder Survey (J-MAPS) Mission,
213th AAS meeting, Long Beach, California, January 2009
Bull. Amer. Astron. Soc. 41, No. 1, 344, 2009, #451.01
[09] Lindegren, L. et al. (2008),
The Gaia mission: science, organization and present status,
in proceed. IAU Symp.248, p.217, Cambridge Univ.Press
Eds. W.Jin, I.Platais, M.A.C.Perryman; see also:
ESA/Gaia home page: www.rssd.esa.int/gaia
[10] SIM Lite Astrometric Observatory,
JPL January 2009, request from Daryl.Victor@jpl.nasa.gov,
see also planetquest.jpl.nasa.gov/SIM
[11] Unwin, S. et al. (2008),
Taking the measure of the universe: precision astrometry with SIM,
PASP 120, 38
[12] Goullioud, R., Catanzearite, J. (2008),
Looking for Earth-like Planets with the SIM Planet Quest Light Mission,
IEEE 1-4244-1488-1/08