RADIOTELESCOPE DE NANÇAY - FORT
NANÇAY RADIO TELESCOPE - FORT

Technical information - October 2006


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 DEC Unix 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.

The support page is now located at:
http://nrt.obspm.fr/

The old support page is :
http://www.obs-nancay.fr/nrt/obsrt.htm


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), Patrick.Thivrier (scheduler). We suggest that any new user of the NRT contacts one of the persons above.


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.