The Telescopi ROBotic de ARas (TROBAR) is a new robotic facility built at
Aras de Los Olmos (Valencia-Spain). This is a 60cm telescope equipped with a
4kx4k optical camera, corresponding to 30x30 arcmin2 FoV, and it will be
primarily used for a systematic search of Ha emitting stars in the Galactic
Plane to a depth of ~14mag. Both data acquisition and reduction will be
performed automatically. The robotization of data acquisition is now entering
its final phase while the development of the data reduction pipeline has just
started.Comment: 10 pages, 3 figures. Accepted for publication in Advances in
  Astronomy - Robotic Astronomy special issu

Stefanon, Mauro

English

arXiv

Mauro Stefanon

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Hindawi Publishing Corporation
Advances in Astronomy
Volume 2010, Article ID 785959, 4 pages
doi:10.1155/2010/785959
Research Article
The Software for the Robotization of the TROBAR Telescope
Mauro Stefanon
Edifici Instituts d’Investigacio´ Pol´ıgon La Coma, Observatori Astronomic Universitat de Vale´ncia, Paterna, 46980 Vale´ncia, Spain
Correspondence should be addressed to Mauro Stefanon, mauro.stefanon@uv.es
Received 26 June 2009; Accepted 30 October 2009
Academic Editor: Taro Kotani
Copyright © 2010 Mauro Stefanon. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
The Telescopi ROBotic de ARas (TROBAR) is a new robotic facility built at Aras de Los Olmos (Valencia, Spain). This is a 60 cm
telescope equipped with a 4 k × 4 k optical camera, corresponding to 30 × 30 arcmin2 FoV, and it will be primarily used for a
systematic search of Ha emitting stars in the Galactic Plane to a depth of ≈14 mag. Both data acquisition and reduction will be
performed automatically. The robotization of data acquisition is now entering its final coding phase while the development of the
data reduction pipeline has just started.
1. Introduction
Galactic Hα emitting objects are tracers of pre- and
postmain-sequence stars as well as of nebulae, cataclysmic
variables, Be stars, and other more exotic objects like Lumi-
nous Blue Variables (LBVs) and Wolf-Rayet stars. IPHAS [1–
4], the most complete survey of the galactic plane carried
out so far, is complete in the magnitude range r′ = 13 to
20 for −5 < |b| < 5. The classical surveys, mostly based on
objective-prism photographic observations, are complete up
to magnitude 9 (see, e.g., [5, 6]). In this context, the main aim
of our project is to carry out a photometric survey covering
the existing gap down to r′ ≈ 14 with observations and data
reduction automatically performed.
2. Telescope and Location
TROBAR is located at the Observatori Astronomic de Aras
(OAA), approximately 100 Km north-west of Valencia, at
an altitude of 1330 m, in a region of low light pollution.
The telescope, realized by Teleskoptechnik Halfmann, has a
main mirror of 60 cm in diameter, with a classical Ritchey-
Chre´tien optical scheme; a Nasmyth focus is present, to
which an optical camera is attached. The telescope can
slew as fast as 10 deg/sec allowing to point any region of
the sky in less than a minute. A filterwheel hosts standard
Sloan u, g, r, i, z, Stro¨mgren u, b, y, v plus two Hα filters
(one narrow and one medium-band). Table 1 lists the main
features of the telescope.
Low level control of telescope pointing capabilities is
done by the Pilar software provided by 4Π Systems Gmb
company, which supplies a socket interface to the TCS
commands.
The optical detector is a Fairchild Peregrine 486 back-
illuminated CCD, providing an array of 4096 × 4096 pixels
of 15 μm × 15 μm read by four amplifiers; the readout noise
is 4e−.
The telescope can be both remotely controlled and
robotically operated and a set of commands also allows to
perform almost all the operations via scripting procedure.
Here we will outline its robotic capabilities.
3. System Description
The operations which can be performed by the telescope
comprise the acquisition of calibration frames (bias, darks,
sky flat field, and focus) and the observation of scientific
targets.
All the software is written in python, with the Object
Oriented paradigm. All astronomical calculations are per-
formed through the pyephem libraries (http://rhodesmill
.org/pyephem/).
The routine operations are managed by a set of 3 main
programs, in communication one with the other through
TCP/IP connection. The adoption of the TCP/IP paradigm
allows a complete independence of the software from the
running machine, hence allowing fast replacing of hardware
in case of problems. These high level programs communicate
2 Advances in Astronomy
Table 1: TROBAR main features.
Device Value
M1 diameter 60 cm
Focal length 4800 mm
Mount Alt-az—Nasmyh focus
Camera Fairchild 4K× 4K optical camera
FoV 30′ × 30′
Filters Sloan u, g, r, i, z; Stro¨mgren u, b, v, y; Hα
(narrow + medium band)
with low-level processes managing the corresponding device
(see Figure 1).
The organization into three main programs directly
reflects what are the main duties an autonomous observatory
should accomplish, namely, check meteorological condi-
tions, safely manage the dome opening and, when all the
conditions are good enough, send an observation to the
telescope. In the following sections the realization of each one
of these processes will be described.
3.1. Meteorology Manager. Meteorological information is
collected by a DAVIS Vantage Pro meteorology station,
installed on a pillar located 10 m away from the dome; it is
equipped with sensors for measuring air pressure, inner and
outer air temperature and relative humidity, wind speed and
direction, solar radiation and rain rate.
Meteorological data is collected by a dedicated process,
called meteo man. This program reads the meteorology
station every 5 minutes during the day and every minute
during the night. Apart from reading data, it also checks if
current meteorological conditions are to be considered safe
for operations; this requirement is achieved when all the
following conditions are satisfied
(i) External humidity must be below 85%.
(ii) Diﬀerence between the dew point and current exter-
nal temperature as absolute value must be grater than
3 degrees Celsius.
(iii) Wind speed must not exceed 15 m/s. If the speed
is between 12 m/s and 15 m/s then an azimuth
limitation flag is raised, meaning that the telescope
should avoid to point directly into the wind and to
the 180 degrees around it.
(iv) Atmosferic pressure must be above 870 hPa.
(v) Rain rate must be equal to zero.
If any of the above conditions is not satisfied, then the
bad meteo condition flag is raised. Since the evaluation of
safe meteorological conditions is a very delicate task for any
autonomous robotic telescope, particular prudence has been
implemented in the algorithm evaluating the meteorological
conditions. Thus, when conditions are not satisfied, in order
to consider meteorological conditions good again, these
must satisfy for 30 minutes the above rules with stronger
constraints, namely, humidity must stay below 80%, wind
speed below 12 m/s, pressure above 880 hPa and, of course,
no rain.
Low-level
camera
control
Camera
manager
Observation
manager
Dome
manager
Low-level
dome
control
Meteo
manager
Local
meteo
station
Ceamet
meteo
station
Figure 1: Flux diagram of the main cycle of the observation
manager.
3.2. Dome Manager. The enclosure of the telescope is a
classical hemispheric dome with two vertical sliding doors.
The dome can rotate at a maximum speed of 6 degrees per
second, which, during the pointing, translates to an average
delay of 30 seconds respect to the telescope, so that the
pointing of the telescope is poorly aﬀected by the dome and
it is not a concern at all for the scope of the scientific project.
The program dome man, which is in charge of managing
the dome has two main duties.
(i) To provide a socket interface to the dome actions:
although for robotical operations the dome is kept
synchronized to the telescope position, so that it is
not necessary to reposition the dome before each
observation, its status is continuously monitored by
another process, running on a diﬀerent machine,
which detects malfunctions and informs the team
accordingly.
(ii) As autonomous process, it continuously acquires
the meteorological conditions and decides to open
or close the dome depending on meteorological
conditions and sun altitude. Currently, the dome is
allowed to stay opened when the sun in below −5
degrees of altitude.
3.3. Observation Manager. The third main process, obs man,
is the one which is in charge of managing the observations.
Figure 2 shows the diagram of the main activities. The
system continuously checks if there is a target suitable for
observations, if meteorological conditions are fulfilled and
if the dome is open. If this is the case, then the observation
process starts. This is composed of two threads, one checking
the tracking status of the telescope during all the exposure
Advances in Astronomy 3
Observation
condition check
thread
Compute
schedule
Check meteo
Check
target obsrevability
Check
dome status
Send target
TCS check
thread
Validate target
Figure 2: Flux diagram of the main cycle of the observation
manager.
and the other checking that all the environmental conditions
are valid during the whole observation.
Due to a limitation in the low level software controlling
the camera provided by the camera company, it is currently
not possible to interrupt an ongoing observation. The
information collected by the two threads is then used at the
end of the exposure for validating the observation; if at least
one of the two threads reported an error, then the target is
ingested back into the archive for subsequent reobservation.
Although the scheduling software already takes into
account constraints whose dissatisfaction can reveal dan-
gerous for the telescope, the observation manager, before
starting each target, performs a bunch of checks which
prevent the telescope from directly pointing towards the sun,
the moon and towards those directions which cannot be
reached by the telescope and would thus send the telescope
to its limit switches.
Each one of the above processes is coupled to an
isAlive program. This is a crontab regulated job periodically
checking that the corresponding process is running and, if
this is not the case, restarting it.
3.3.1. Target Archive and Scheduling. The set of targets is
organized in a MySQL table. Each target can be associated
to a user-defined priority value with the logic that the lowest
is the value, the highest is the priority; in addition the
definition of all the most common constraints under which
each target should be observed, such as the maximum moon
fraction and distance, minimum and maximum airmass, and
periodicity of observation is implemented.
The fundamental idea behind the scheduling algorithm is
to try to observe each target when it is closest to its minimum
airmass (either because it is transiting through the meridian
or because the user set a greater value in the minimum
airmass field). This is achieved in the following two steps:
(i) the scheduling software makes a first pass through all
the targets, selecting only those whose constrains are satisfied
from that moment and through all the exposure time;
(ii) a figure of merit (FoM) is then applied to each of
the selected targets. This FoM is a generalization of the e−|x|
mathematical function, where x here stands for the whole
set of parameters. This is done in order to have a strong
peak when all the conditions are best satisfied. The complete
adopted function is
h
(
p, fa, ft, fd
) = p
⎛
⎝1− exp
⎛
⎝−
(
fa
ft
)1/2⎞
⎠ + fd
⎞
⎠, (1)
where p ∈ N is an integer number specifying the priority,
with the value of 0 denoting the highest priority; the
normalized diﬀerence between the current and the minimum
airmass fa is given by
fa = a(0)−min(a)min(a) , (2)
where a(0) is the airmass at the time of the computation
and min(a) is the maximum between the minimum airmass
the object can reach on the sky and the user requirements
for the minimum airmass; ft is the ratio between the total
time an object is above its horizon (as define by the airmass
constraints) and the required exposure time. Finally fd is
the normalized distance of the object from the celestial pole.
Explicitely, the expression for fd is
fd = n(δ −min(δ))90.0−min(δ) . (3)
Here δ is the declination of the object, min δ is the minimum
declination which is visible from the site for a given airmass,
and is n a factor to reduce fd values to a suitable range of
values of the whole h function.
The fd term has the eﬀect of giving higher priority to
those objects with low declination, which typically are the
objects whose time for observation is shorter than that of
objects at higher declinations. Finally, the 1/2 exponent to the
argument of the exponential function has been introduced in
order to smooth the wings of the FoM.
Figure 3 shows the value of the result of applying the
FoM described above to three targets with the same Right
Ascension but with Declination δ = +10, +30, and +60,
respectively.
Note that targets with p = 0 will always have the lowest
value of h (in fact h ≡ 0 independently of the value of
4 Advances in Astronomy
0
0.01
0.02
0.03
0.04
0.05
0 2 4 6
Fo
M
(a
rb
it
ra
ry
u
n
it
s)
Time (hours past sunset)
Figure 3: Scheduler FoM for objects with the same priority = 1,
RA = 15h and δ = +10, +30, and +60 for red dot-dashed, green
solid and blue long dashed line, respectively.
the other constraints), which translates into allocating the 0-
priority target as soon as possible.
The FoM expression can of course be generalized by
introducing multiplicative parameters with the eﬀect of
shifting in time the points where the FoMs of targets with the
same RA but diﬀerent δ intersect (cf. Figure 3), in order to
better suite arising scheduling needs. This optimization will
be done during the commissioning phase.
3.4. Hardware. All the software runs on almost of the
shelf hardware, without any particular need for high-speed
processing, with a total number of three computers. The only
exception is the machine with the obs man program which
is running on a quad-core linux. This is due not because of
the supposedly high demanding software of the observation
manager, but because this machine is shared with another
experiment which need real-time data analysis.
In addition, each machine has its own UPS system
granting power supply to the computers in case of shortages.
A UPS for the dome is also foreseen to be installed in the near
future.
4. Current Status and Future Prospects
The coding is now complete at the 80% level and we foresee
to complete it by the end of the year. In particular one
of the tasks we still need to implement is the procedure
of automatic focusing. This will be achieved by a single
exposure, tentatively at the beginning of the night, on which
a bright star is imaged with diﬀerent focus oﬀset and by
slightly moving the telescope between one acquisition and
the next. The image will then be analyzed using SExtractor
[7] and the fwhm of the star fitted by a parabola.
In parallel we started to develop a pipeline for the
reduction of the survey data. This will make extensive use
of the pyraf environment for the prereduction processes
(bias subtraction, flat field correction, etc.). Detection of
the objects on each image will be managed by SExtractor;
its mag auto value will be used as a first estimation of the
flux, which will then be used by DoPhot [8] to derive psf
magnitudes.
5. Conclusions
We described the software for the robotization of TROBAR,
with the aim of performing a survey of the Galactic Plane,
looking for Hα emitting objects. The system is able to allocate
and observe the targets in a MySQL archive when they are
best visible and depending on observing constraints. The
code is now almost complete and we foresee to start robotic
operations by the end of the present year.
References
[1] J. E. Drew, R. Greimel, M. J. Irwin, et al., “The INT Photometric
Hα survey of the northern Galactic plane (IPHAS),” Monthly
Notices of the Royal Astronomical Society, vol. 362, no. 3, pp.
753–776, 2005.
[2] M. Corradi, R. Rodrı´guez-Flores, A. Mampaso, et al., “IPHAS
and the symbiotic stars: I. Selection method and first discov-
eries,” Astronomy & Astrophysics, vol. 480, no. 2, pp. 409–419,
2008.
[3] A. R. Witham, C. Knigge, J. E. Drew, et al., “The IPHAS
catalogue of Hα emission-line sources in the northern Galactic
plane,” Monthly Notices of the Royal Astronomical Society, vol.
384, no. 4, pp. 1277–1288, 2008.
[4] E. A. Gonza´lez-Solares, N. A. Walton, R. Greimel, et al., “Initial
data release from the INT Photometric Hα survey of the
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Astronomical Society, vol. 388, no. 1, pp. 89–104, 2008.
[5] L. Kohoutek and R. Wehmeyer, “Catalogue of H-alpha emission
stars in the Northern Milky Way,” Astronomy and Astrophysics
Supplement Series, vol. 134, no. 2, pp. 255–256, 1999.
[6] L. R. Wackerling, “A catalogue of early-type stars whose spectra
have shown emission lines,” Monthly Notices of the Royal
Astronomical Society, vol. 149, p. 405, 1970.
[7] E. Bertin and S. Arnouts, “SExtractor: software for source
extraction,” Astronomy and Astrophysics Supplement Series, vol.
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photometry program: description and tests,” Publications of the
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The Software for the Robotization of the TROBAR Telescope

The Telescopi ROBotic de ARas (TROBAR) is a new robotic facility built at
Aras de Los Olmos (Valencia, Spain). This is a 60 cm telescope equipped with a 4k×4k optical camera, corresponding to 30×30 arcmin2 FoV, and it will be primarily used for a systematic search of Ha emitting stars in the Galactic Plane to a depth of ≈14 mag. Both data acquisition and reduction will be performed automatically. The robotization of data acquisition is now entering its final coding phase while the development of the data reduction pipeline has just started

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