Astrometry at the RTT150 telescope within the international collaboration between KSU (Russia), TUG (Turkey), and NAO (Ukraine)
Modern astrometric projects require precise positional measurements of objects down to magnitude 20m–22m. For ground-based observations, this is possible by the use of astrographs with apertures 1 meter or more with precise tracking using long exposures and precise timing. The multifunctional astron...
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| Zitieren: | Astrometry at the RTT150 telescope within the international collaboration between KSU (Russia), TUG (Turkey), and NAO (Ukraine) / Z. Aslan, I.M. Khamitov, R.I. Gumerov, A.A. Ibragimov, A. Nemtinov, A.V. Ivantsov, L.A. Hudkova, G.I. Pinigin, A.V. Shulga // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 523-527. — Бібліогр.: 11 назв. — англ. |
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irk-123456789-797142015-04-04T03:01:58Z Astrometry at the RTT150 telescope within the international collaboration between KSU (Russia), TUG (Turkey), and NAO (Ukraine) Aslan, Z. Khamitov, I.M. Gumerov, R.I. Ibragimov, A.A. Nemtinov, A. Ivantsov, A.V. Hudkova, L.A. Pinigin, G.I. Shulga, A.V. MS6: New Trends, Research Directions, and Perspective Programs in the Field of Astronomy and Astrophysics Modern astrometric projects require precise positional measurements of objects down to magnitude 20m–22m. For ground-based observations, this is possible by the use of astrographs with apertures 1 meter or more with precise tracking using long exposures and precise timing. The multifunctional astronomical complex RTT150 (the 1.5-m Russian–Turkish Telescope) is appropriate for such purposes. 2005 Article Astrometry at the RTT150 telescope within the international collaboration between KSU (Russia), TUG (Turkey), and NAO (Ukraine) / Z. Aslan, I.M. Khamitov, R.I. Gumerov, A.A. Ibragimov, A. Nemtinov, A.V. Ivantsov, L.A. Hudkova, G.I. Pinigin, A.V. Shulga // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 523-527. — Бібліогр.: 11 назв. — англ. 0233-7665 http://dspace.nbuv.gov.ua/handle/123456789/79714 en Кинематика и физика небесных тел Головна астрономічна обсерваторія НАН України |
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MS6: New Trends, Research Directions, and Perspective Programs in the Field of Astronomy and Astrophysics MS6: New Trends, Research Directions, and Perspective Programs in the Field of Astronomy and Astrophysics |
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MS6: New Trends, Research Directions, and Perspective Programs in the Field of Astronomy and Astrophysics MS6: New Trends, Research Directions, and Perspective Programs in the Field of Astronomy and Astrophysics Aslan, Z. Khamitov, I.M. Gumerov, R.I. Ibragimov, A.A. Nemtinov, A. Ivantsov, A.V. Hudkova, L.A. Pinigin, G.I. Shulga, A.V. Astrometry at the RTT150 telescope within the international collaboration between KSU (Russia), TUG (Turkey), and NAO (Ukraine) Кинематика и физика небесных тел |
| description |
Modern astrometric projects require precise positional measurements of objects down to magnitude 20m–22m. For ground-based observations, this is possible by the use of astrographs with apertures 1 meter or more with precise tracking using long exposures and precise timing. The multifunctional astronomical complex RTT150 (the 1.5-m Russian–Turkish Telescope) is appropriate for such purposes. |
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Article |
| author |
Aslan, Z. Khamitov, I.M. Gumerov, R.I. Ibragimov, A.A. Nemtinov, A. Ivantsov, A.V. Hudkova, L.A. Pinigin, G.I. Shulga, A.V. |
| author_facet |
Aslan, Z. Khamitov, I.M. Gumerov, R.I. Ibragimov, A.A. Nemtinov, A. Ivantsov, A.V. Hudkova, L.A. Pinigin, G.I. Shulga, A.V. |
| author_sort |
Aslan, Z. |
| title |
Astrometry at the RTT150 telescope within the international collaboration between KSU (Russia), TUG (Turkey), and NAO (Ukraine) |
| title_short |
Astrometry at the RTT150 telescope within the international collaboration between KSU (Russia), TUG (Turkey), and NAO (Ukraine) |
| title_full |
Astrometry at the RTT150 telescope within the international collaboration between KSU (Russia), TUG (Turkey), and NAO (Ukraine) |
| title_fullStr |
Astrometry at the RTT150 telescope within the international collaboration between KSU (Russia), TUG (Turkey), and NAO (Ukraine) |
| title_full_unstemmed |
Astrometry at the RTT150 telescope within the international collaboration between KSU (Russia), TUG (Turkey), and NAO (Ukraine) |
| title_sort |
astrometry at the rtt150 telescope within the international collaboration between ksu (russia), tug (turkey), and nao (ukraine) |
| publisher |
Головна астрономічна обсерваторія НАН України |
| publishDate |
2005 |
| topic_facet |
MS6: New Trends, Research Directions, and Perspective Programs in the Field of Astronomy and Astrophysics |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/79714 |
| citation_txt |
Astrometry at the RTT150 telescope within the international collaboration between KSU (Russia), TUG (Turkey), and NAO (Ukraine) / Z. Aslan, I.M. Khamitov, R.I. Gumerov, A.A. Ibragimov, A. Nemtinov, A.V. Ivantsov, L.A. Hudkova, G.I. Pinigin, A.V. Shulga // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 523-527. — Бібліогр.: 11 назв. — англ. |
| series |
Кинематика и физика небесных тел |
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| fulltext |
ASTROMETRY AT THE RTT150 TELESCOPE
WITHIN THE INTERNATIONAL COLLABORATION
BETWEEN KSU (RUSSIA), TUG (TURKEY), AND NAO (UKRAINE)
Z. Aslan1, I. M. Khamitov1, R. I. Gumerov2, A. A. Ibragimov2, A. Nemtinov2,
A. V. Ivantsov3, L. A. Hudkova3, G. I. Pinigin3, A. V. Shulga3
1TUBITAK National Observatory
Akdeniz Universitesi Yerleskesi, 07058 Antalya, Turkey
e-mail: aslan@tug.tug.tubitak.gov.tr
2Astronomical Observatory, Kazan State University
18 Kremlyovskaya Str., 420008 Kazan, Russian Federation
e-mail: rgumerov@ksu.ru
3Research Institute “Nikolaev Astronomical Observatory”, MES of Ukraine
1 Observatorna Str., 54030 Mykolaiv, Ukraine
e-mail: pinigin@mao.nikolaev.ua
Modern astrometric projects require precise positional measurements of objects down to mag-
nitude 20m–22m. For ground-based observations, this is possible by the use of astrographs with
apertures 1 meter or more with precise tracking using long exposures and precise timing. The multi-
functional astronomical complex RTT150 (the 1.5-m Russian–Turkish Telescope) is appropriate for
such purposes.
THE RUSSIAN–TURKISH TELESCOPE RTT150
The 1.5-m telescope RTT150 was manufactured by the well-known optical-mechanical company LOMO
(St.-Petersburg) and was moved after 1995 to Turkey [1, 6, 11]. In 1998 the work on the telescope’s as-
sembly and installation in Antalya has been completed and a Joint Facility of the Kazan State University
(KSU), the Space Research Institute of the Russian Academy of Sciences (SRI RAS), and the Turkish National
Observatory (TUG) was ready to provide for scientific research.
The optical scheme of the RTT150 telescope has a set of four optical systems (F/3, F/8, F/16 for the Casseg-
rain focus and F/48 for the Coude focus). In addition, the telescope is equipped with two guides – Ritchey–
Chretien telescopes – with 360 mm diameter mirrors, which can be used independently. The full FOV of
the Ritchey–Chretien F/8 variant with the corrector installation is 88 arcminutes (300 mm). For the small field
(8′×8′) limited by the CCD size, the corrector is not necessary.
RTT150 is equipped with three CCD cameras, which give a possibility to perform observations in stare mode
and in drift scan one.
The main camera is the ANDOR CCD (2K×2K, a pixel size is 13.5×13.5 mkm, CCD scale is 0.23′′/pixel).
With this CCD camera, it has been possible to obtain images of the magnitude 22m stars with 10 minute
exposures; objects down to magnitude 20m with 5 minute exposures are registered with a good signal/noise
ratio.
The other two cameras, ST-8 and AP-47 (APOGEE), are the auxiliary ones of lesser sizes and lower sensi-
tivities. ST-8, which is completed with an AO7 device, has so far been used as a photo guider. We note that,
with this device, it was possible to record images with FWHM of 0.7–0.9 arcseconds in short exposures (up
to 10 min). AP-47 will soon replace ST-8 as a guider and ST-8 can be attached to one of the 360 mm guide
telescopes.
For longer exposure times, the new digital CCD camera DinaCam with a liquid nitrogen cooling could be
used. This camera was developed at the Special Astrophysical Observatory. In addition to its extremely low
noise, the camera provides several modes of charge storage: stare mode, drift scan, forward-backward and their
combination. The DinaCam CCD camera is equipped with the ISD017AP CCD.
c© Z. Aslan, I. M. Khamitov, R. I. Gumerov, A. A. Ibragimov, A. Nemtinov, A. V. Ivantsov, L. A. Hudkova, G. I. Pinigin,
A. V. Shulga, 2004
523
The precise automatic drive mode of the telescope along a predicted trajectory is used to take images of
faint objects in long exposures with the aim to decrease distortions of images of asteroids. A possibility for
precise tracking is recognized for telescope motion along the predicted trajectory, which is successfully used to
correct irregularities of the general gear and to compensate the influence of differential refraction at great zenith
distances.
The telescope is equipped with the computer control system developed at the KSU and SRI RAS that allows
one to perform observations:
– in batch mode, when the list of objects (coordinates, moments of the start of an exposure, and exposure
times) is prepared in advance and loaded into the computer control for pointing the telescope on the next
target;
– via the remote terminal (PC), connected to the control PC, and (using the Internet) via local network.
The computer control software has a user-friendly interface which allows one to control the telescope both
in interactive and automatic modes for performing observations in accordance with the prepared list of objects.
OBSERVATION PROGRAMS
The main task of the RTT150 telescope is the astrophysical research: observations of distant objects (quasars,
galaxies and clusters of galaxies, micro-lensing objects, etc.), the nearby galaxies and the Milky Way objects.
However, the RTT150 with its equipment for a high quality imaging allow one to use the telescope for modern
astrometry. Observations of extra galactic radio sources (ERS) and stars around them have been successfully
made within an international campaign for the refinement of the connection between optical and radio coordinate
systems (2000–2003). Some observations have been also carried out for selected minor objects of the Solar System
(2002–2003) with the aim to determine their positions.
At present, a list of the observation programs and methods is prepared for new astrometric projects. In par-
ticular, several problems concerning the research of the Solar System small bodies down to magnitude 20m are
started, such as
– determination and improvement of orbital elements of near-Earth asteroids (NEAs),
– determination of masses of selected asteroids by taking into account their gravitational perturbations on
orbits of the less massive asteroids,
– participation in gathering precise positions of selected minor planets for ground-based support of the in-
ternational program “GAIA Follow-Up”, and photometric observations of brief occultations of stars by
asteroids.
A FOLLOW-UP PROGRAMME FOR THE SPACE ASTROMETRY PROJECT GAIA
This program relates only to the astrometric aspect of the GAIA project for the Solar System object [9, 10].
GAIA will provide many position measurements of objects of the Solar System with the unique precision. About
one million small objects in our Solar System, mainly asteroids, will be observed down to magnitude 20m.
The highest precision, about 10 micro arcseconds, will be reached for stellar objects with magnitude brighter
than 15m. It will be about 200μ as for those of magnitude 20m. This precision will, however, be degraded for
the non-stellar and fast-moving objects, such as NEAs. It could then be about several mas. GAIA will perform
a wide scan of the sky and will have not generally the possibility of immediately re-observing an object just
detected. The faint and eventually fast objects are then likely to be lost.
Therefore, observations on alert seems to be necessary in order to catch more data on these targets and follow-
up from the ground. A follow-up program will be necessary to ensure these objects are not lost and to improve
their ephemerides. Several means make it possible to organize these observations, in particular, dissemination
of alarms by the Internet via mailing lists (Minor Planet Mailing List for example) or maintenance of the official
page of targets. Within the Solar System Working Group of GAIA, the plans are to constitute a network for
ground-based observations in order to follow-up GAIA observations with the principal aim of confirming new
target detections by GAIA and to carry out any astrometric measurements necessary for the improvement of
the orbital elements and the cataloguing of these objects.
Once a network has been organized, it will then be possible, during the years before GAIA launch in about
2010, to test the astrometric performances on representative targets, to set up operations of data recovery, to
develop and check a procedure for astrometric reductions, and then to prepare some experiments on full-scale
alarms. Particularly, it will provide many positional measurements of the Solar System objects; also numerous
524
new objects will be detected. Some constraints imposed by the objectives of the GAIA follow-up network are
available in [Thuillot W., Stavinschi M., private communication].
For the proposed network, small telescopes down to 1.5-m seem to be well suitable for follow-up task. Fast
moving objects such as NEAs will require fast reactions in order to operate several telescopes after receiving
an alert from the GAIA control centre. Ground based robotic or automatic telescopes would obviously be much
more efficient in order to shorten the reaction time. Besides, small telescopes are able to work in appropriate
locations. At present, there are already identified more than 10 telescopes which are interested in this program.
In the near future, this network will be extended and a process established to make it efficient for a follow-up:
identification of each limiting magnitude, determination of the individual astrometric accuracy, rules to apply for
a fast reaction on alert. Also, CCD cameras on these telescopes are generally well suited for precise astrometry
of fast and eventually faint objects. The telescope RTT150 could also be used for monitoring the objects down
to 20m.
CURRENT PROGRAMMES FOR COLLABORATING TELESCOPES
Within the joint project on the basis of international collaboration of KSU (Russia), TUG (Turkey) and Nikolaev
Astronomical Observatory – NAO (Ukraine), it is planned to perform positional and photometric observations of
the Solar System small bodies in connection with GAIA project [2]. A fundamental problem for determination
and improvement of the orbits and also for studying the multiplicity and masses of the selected asteroids
down to magnitude 20m is picked out within the project framework on the base of precise observations at
the 1.5-m telescope RTT150.
In addition, observations of the brighter objects (down to 18m) will be carried out with the CCD telescopes of
NAO such as AMC (D = 190 mm, F = 2480 mm, CCD scale is 1.33′′/pixel), MCT (D = 160 mm, F = 2046 mm,
CCD scale is 1.61′′/pixel), FRT (D = 300 mm, F = 1500 mm, CCD scale is 2.19′′/pixel). In 2001–2003,
the telescopes AMC, MCT, FRT of NAO were modernized and equipped with perfect Universal CCD cameras
(UCC) and necessary software for observations to implement the whole range of possibilities for high-accuracy
observations of stars and asteroids.
The joint use of telescopes with different limiting magnitudes and different CCD fields of view will allow
position measurements of the Solar System’s faintest star-like or slow moving bodies with the highest precision
in small fields (8′×8′ for RTT150), and fast-moving objects with high precision in wide fields (about 30′×30′
for NAO telescopes).
During the period of implementation of the project (within the next 5 years) at the collaborating telescopes,
there will be observed
– about 80 asteroids down to magnitude 20m, which will be NEAs at distances less than 0.1 AU, allowing
the determination and improvement of their orbital elements,
– about 100 asteroids with encounters, allowing the inclusion of task of mass determination in a program
before GAIA.
First observations of objects from the prepared list have begun in May 2004 at the RTT150. From 82 ob-
servations of three minor planets and one NEA during one night, the mean error of a single observation was
evaluated using (O–C) values, to be in the range 0.02′′÷0.04′′ in both coordinates. Also, mean errors in the range
0.01m ÷ 0.08m for a single observation were obtained using V (O–C) values. An accuracy obtained shows a high
potential for such observations at the RTT150. In general, by using reference catalogues which have a high
accuracy and density (TC2, UCAC, USNO-B1, etc.) the expected positional accuracy of the Solar System small
bodies down to magnitude 20m, including fast and non-stellar asteroids in the near-Earth space, will be about
0.02′′ ÷ 0.1′′.
The use of contemporary ephemerides and TV CCD cameras for observations of occultation of stars by
asteroids provides a new possibility to study dynamical and physical characteristics of the Solar System bo-
dies. Such observations will not only allow to improve the accuracy of observed quantities, but will also give
an opportunity to study the physical properties of the surfaces, to determine diameters, to study resolvable
objects, etc.
Determination of an enough precise orbit of a single asteroid (in the case of NEA – its trajectory) is well
known and approved. In the case of a binary asteroid, the problem is much complicated, because the rotation of
the components would affect the visible motion of separate parts of the binary asteroid. That’s why it is planned
to pay some attention for detection of possible satellites of asteroids (detection of binarity). Here we intend
to combine exposures of the direct imaging with observations of occultation of stars by asteroids and careful
photometric monitoring of the assumed resolvable binaries. For improving the ephemerides, it is planned to use
fast photometry of the occultations besides astrometric methods. For this purpose, RTT150 will be equipped
with a fast photometer for observation of occultations.
525
One of the important characteristics of asteroids is their masses. It is planed to evaluate masses of some
asteroids using the dynamical method, based on the analysis of perturbations of small asteroids by big ones.
It is considered that such a method gives the smallest relative error. As shown by A. Fienga et al. [5] GAIA
will allow more than 100 asteroid masses to be determined accurately.
METHODS
It is planned to use the method and experience of CCD observations that have been gained during the observa-
tional program of extragalactic radio sources (stare mode). It is possible for asteroid observations in drift scan
mode to use the covered strips method [6, 7] and the combined CCD method [4, 8].
The covered strips method
The first and basic objective of the method is to get a direct image of asteroids with reference stars. With
the availability of a reference catalogue of an enough density and accuracy (TC2, UCAC, USNO-B1), the task
to calculate object coordinates with the RTT150 observations can be fulfilled successfully.
However, there can be lacks of reference stars in some fields of celestial sphere. In this case, the auxiliary ob-
servations at the precise meridian circle AMC NAO can be used to get additional reference stars. For the method
of covered strips, a CCD detector is used in drift scan mode. The method is effective for observations of the Solar
System small bodies down to magnitude 20m by performing multiple CCD observations at the RTT150 and
other telescopes within the project. Thereby, the observations of asteroids at the RTT150 are combined with
the AMC observations and the data are obtained in strip-scans of an enough length with the aim to include
reference stars from precise catalogues, besides asteroids [6, 7]. The use of this method for our observations in
2002–2003 has given positive results.
The combined CCD method
The use of CCD cameras in two modes (stare and drift-scan) is planned for different optical channels of
the RTT150 by applying the combined CCD method [4, 8].
The combined CCD method of observations of NEAs or other small bodies is a new approach by using
techniques and methods to study characteristics of a motion, which can provide a high positional accuracy.
The principle of observation at the telescope with equatorial mounting, equipped with a multipurpose CCD
camera is in the base of this method. The CCD camera has the possibility to record celestial objects both in
stare and drift scan mode, i.e., small bodies are observed in stare mode with the fixed telescope, and moving
star images are obtained in drift scan mode. So, we have stellar images both for small bodies and for reference
stars with the moments of observations recorded with the aid of the time service. The combined method was
successfully used for observation of objects on geosynchronous Earth orbits [3].
CONCLUSIONS
Technical parameters of the RTT150 and the first observations of the selected asteroids have shown that it is
possible to determine high-precise coordinates of such objects, with an accuracy in the range of 20–40 mas,
which satisfies the requirements of the GAIA Follow-UP Program.
A network of the automatic telescopes, together with the narrow-field CCD and wide-field CCD, can be
used for coordinated and precise observations of the Solar System bodies before GAIA is launched, or during
the mission in alert mode.
Acknowledgements. The authors highly appreciate the fruitful discussion with William Thuillot about
the GAIA mission and the follow-up programme.
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