RADIOTELESCOPE
DE NANÇAY - FORT
NANÇAY RADIO TELESCOPE - FORT
Technical information - April 2019
The Nançay Radio
Telescope :
The instrument can observe any source at declination DEC > -
39°. This is a transit instrument, for which the maximum
integration time per day for a source at DEC = 0° is typically
about one hour (ON + OFF) ; this time increases as 1/cos (DEC)
(whereas the efficiency decreases).
The focal
and receivers systems (FORT = Foyer Optimisé pour le
RadioTélescope):
Two receivers are available, allowing a continuous frequency coverage.
The Low Frequency system (1.1-1.8 GHz) provides optimum characteristics
for the HI 21 cm and OH 18 cm lines. The High Frequency system
(1.7-3.5 GHz) includes the 9 cm lines. The corrugated horns can be
rotated by ±90°. Up to two linear plus two circular
polarizations can be recorded simultaneously. Cross-polarization and
complete Stokes parameters are available for the Low Frequency system
in a limited configuration (some L.O.s have a fixed value); their
extension and precision improvement are still under development.
Meanwhile, it is recommended to use the horn rotation to extract the
Stokes parameters properly.
The IF bandwidth is 400 MHz. The digital auto-correlator has a
total bandwidth that can be set from 200 kHz to 50 MHz. The 8192
frequency channels should be splitted into at least 2 banks and up to 8
banks. Up to 4 independent frequencies can be recorded
simultaneously. Continuum measurements can be performed through 8
dedicated channels; the frequency and bandwidth corresponds to the
auto-correlator setup. Configuration changes can be programmed to be
performed by the real-time computer even within a single observation.
Beam size
and efficiencies:
The half power beam widths are respectively about : 4’ (RA) x 22’
(DEC), 3.5’ x 19’ and 2’ x 10’ at 21, 18 and 11 cm. The corresponding
point source efficiency at DEC = 0° is about 1.4 K/Jy at 21 cm and
0.8 K/Jy at 11 cm. The efficiency does not show significant variation
between the different polarizations. The system temperatures are about
35 K at 21 and 45 K at 11 cm. The r.m.s. continuum confusion levels due
to background sources are respectively 20, 15 and 7 mJy at 21, 18 and
11 cm. The above values are indicative and are susceptible to be
updated.
Data
handling:
Data reduction can be achieved on the site or remotely with a Linux
workstation. Raw data must be pre-processed with the dedicated
Nançay "NAPS" software. Data reduction can then be performed
with the Nançay "SIR" software, or data can be exported in FITS
format for further processing instead. Shipping of FITS data written on
CD-ROMs can be considered for remote users. Please note that the FITS
export has been tested successfully with the CLASS package, but that
there is still a difficulty when exporting into AIPS++; that option
cannot be guaranteed at the moment.
Web &
e-mail :
Forms and relevant information can be found on the following web pages:
http://nrt.obspm.fr/nrt/obs/rea_rt2.html/
Also at the "Station de Radioastronomie de Nançay":
http://www.obs-nancay.fr/nrt/obs/rea_rt2.htm
NB: The list of the submitted applications and P.I.s is published on
this Nançay web site.
For more information please contact at Meudon campus at internet adresses
@obspm.fr : Pierre.Colom (chairman of the CdP), Eric.Gerard,
Jean-Michel.Martin, (astronomers) ; at Orleans campus at internet adresses
@cnrs-orleans.fr : icognard (astronomer, scientific director) ; or at the
Nançay Radio Telescope at internet adresses @obs-nancay.fr :
Patrice.Lespagnol (computing engineer), Laurence.Alsac (engineer).
We suggest that any new user of the NRT contacts one of the persons above.
It is mandatory for ANY new pulsar application (Ismael Cognard at Orleans) .
The Nançay Radio Telescope and the FORT system are operated by
the Observatoire de Paris with co-funding from the CNRS-INSU and from
the Région Centre.