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The following list of IRAM technical Reports contains reports from IRAM Grenoble or Granada on various topics (technical / informatical / physical / ...) written in English and PS/PDF format.


Year/No.
Report




2009 - 3
A simulator of interferometric On-the-fly observations
Authors:
N. Rodriguez-Fernandez (IRAM), Frederic Gueth (IRAM), Jerome Pety (IRAM)
Keywords: interferometric wide-field imaging, on-the-fly observing, simulations
Abstract: We have developed a simulator of interferometric on-the-fly observations in the framework of our research on image synthesis for mosaics observed in the on-the-fly (OTF) mode, in which the interferometer takes data at the same time that the antennas move continuously across the source. This simulation tool has been developed on the basis of the IRAM/GILDAS ALMA+ACA simulator (Pety, Gueth & Guilloteau 2001).
Download: [ PDF file ].




2009 - 2
Imaging of interferometric On-The-Fly observations (I): context and discussion of possible methods
Authors:
N. Rodriguez-Fernandez (IRAM), Jerome Pety (IRAM), Frederic Gueth (IRAM)
Keywords: interferometric wide-field imaging, on-the-fly observing
Abstract: We discuss the measurement equation for interferometric observations of fields larger than the primary beam of the antennas, both for standard "pointed" mosaics and for mosaics observed in on-the-fly (OTF) mode. The main advantages of using the OTF mode are a gain of observing time and a higher homogeneity of the dataset. OTF mosaicing is similar to classical stop-and-go mosaicing but the effective beam when observing OTF is not exactly the primary beam of the antennas. We show that the effective beam is similar to the primary beam when the scanning rate is better than Nyquist. We review different techniques to image and deconvolve mosaic data, in particular the Ekers & Rots 1979 (ER79) scheme, which consist in Fourier transforming the visibility function with respect to the scanning coordinate. We discuss how to implement an OTF-optimized imaging algorithm to deal with the mosaic data as a whole based on the ER79 scheme. Finally we discuss observing time and mosaic size constrains for OTF observations.
Download: [ PDF file ].




2009 - 1
IRAM-30m EMIR time/sensitivity estimator
Author:
J.Pety (IRAM Grenoble and Observatoire de Paris)
Keywords: IRAM 30-m - EMIR - proposal preparation - time estimator
Abstract: This memo describes the equations used in the IRAM-30m EMIR time/sensitivity estimator available in the GILDAS/ASTRO program. A large part of the memo aims at deriving sensitivity estimate for the case of On-The-Fly observations, which is not clearly documented elsewhere (to our knowledge). Numerical values of the different parameters used in the time/sensitivity estimator are grouped in appendix A.
Download: [ PDF file ].




2008 - 2
Single-dish observation and processing to produce the short-spacing information for a millimeter interferometer
Authors:
N.J. Rodriguez-Fernandez, J. Pety, F. Gueth
Keywords: interferometric wide-field imaging, short-spacings
Abstract: Adding the short-spacing information filtered out by (sub)-millimeter interferometers is crucial to obtain good images of wide fields (observed in stop-and-go or on-the-fly mode). In this memo we discuss how to obtain the short-spacing information with single-dish data using the pseudo-visibility method. We have computed the natural weights of the pseudo-visibilities from the noise in the single-dish map. We also discuss 1) the relative weights of the single-dish and interferometric data, 2) how the relative weight equation transform into relative integration time and 3) severals ways of weighting the pseudo-visibilities. Finally, we discuss the addition of the short-spacings in practice (e.g. single-dish artifacts, field-of-view,...).
Download: [ PDF file ].




2008 - 1
Test Observations of CLOUDSAT
Authors:
D. Morris (IRAM Grenoble), G. Butin (IRAM Grenoble), N. Marcelino (IRAM Granada)
Keywords: IRAM 30m telescope, Cloudsat, receivers, satellite interference
Related Documents:
IRAM Newsletter 63: Cloudsat - consequences for Radio Astronomy
IRAM Newsletter 66: The 30m and the Cloudsat
Abstract: Test observations to assess the risk of interference due to Cloudsat emissions were made at the IRAM 30m telescope in July 2006. The telescope was pointed at various offsets from the predicted culmination of Cloudsat and short integrations were made. A simple axially symmetric model of the antenna sidelobe patterns was used to predict an upper limit to the expected signal. Although interference in the shared band was detected, it is of short duration. In routine astronomical observations its impact can be reduced by telescope pointing restrictions during staellite transits and by avoiding observations when the satellite is near the zenith. The loss of observing time will be small. In this special case (time)sharing between Radioastronomy and an active service is feasible at the price of some loss in observing time. This is possible because only one fast moving satellite with excellent sidelobes in angle and frequency is active.
Download: [ PDF file ].




2005 - 1
CLASS evolution: I. Improved OFT support
Authors:
P. Hily-Blant (IRAM Grenoble), J.Pety (IRAM Grenoble, LERMA Paris), S. Guilloteau (L3AB, Obs. de Bordeaux)
Keywords: CLASS, single-dish telescope software, OTF
Related Document: CLASS manual
Abstract: CLASS is a GILDAS software for reduction and analysis of (sub)-millimeter spectroscopic data. It is daily used to reduce spectra acquired with the IRAM 30m telescope. CLASS is currently used in many other facilities (e.g. CSO, HHT, Effelsberg) and it is considered for use by Herschel/HIFI. CLASS history started in 1983. As a consequence, it was written in FORTRAN 77 and tailored to reduce pointed observations. On-The-Fly support was added in the 90s but it showed limitations as the quantity of OTF data increased quickly. One year ago, we decided to fully rewrite CLASS in FORTRAN 90 with the 3 following goals: 1) clarifying satisfying features with backward compatibility in mind, 2) improving code readability to simplify maintenance and 3) easing reduction of large OTF data sets. This memo is describing the current state of affair with a particular emphasis on changes in the program behavior. Future foreseen changes (linked to the increase of receiver instantaneous bandwidth like an improved conversion from frequency to velocity axis) will be described in a future memo.
Download: [ PDF file ].




2005 - 0
Thoughts about polarization calibration with the next generation receivers at Plateau de Bure
Author:
H. Wiesemeyer (IRAM Grenoble)
Keywords: polarimetry, leakage terms, crossed-band polarization calibration
Related Document: IRAM technical report 2001 - 1
Abstract: With the next generation receivers, the Plateau de Bure interferometer will be able to simultaneously measure all four Stokes parameters. The interferometer can be optimized for the detection of either linear or circular polarization. In both cases, the weakness of the polarization of all bandpass and phase calibrators requires calibration schemes that are more involved than the usual mode. Time estimates are given.
Download: [ compressed PS file ] or [ PDF file ].
2003 - 4
Case for interoperability as an ALMA off-line model
Authors: J. Pety (Obs. de Paris/IRAM Grenoble), F. Gueth (IRAM Grenoble), S. Guilloteau (ESO/IRAM Grenoble), P. Teuben (U. Maryland), M. Wright (RAL, U.C. Berkeley)
Keywords: Interoperability, Offline, Software, Science, Calibration
Abstract: In this memo we argue that interoperability between the existing radio-interferometry packages provides a fast, robust, flexible, complete, and user-friendly data reduction package for ALMA. We discuss our first steps toward interoperation with MIRIAD and GILDAS using python as a command line interface.
Download: [ compressed PS file] or [ PDF file ].
2003 - 3
Complementarity of the AIPS++, GILDAS and MIRIAD packages as seen from evaluations for ALMA off-line processing
Authors: J. Pety (Obs. de Paris/IRAM Grenoble), F. Gueth (IRAM Grenoble), S. Guilloteau (ESO/IRAM Grenoble), P. Teuben (U. Maryland), M. Wright (RAL, U.C. Berkeley)
Keywords: Requirements, Offline, Software, Science, Calibration
Abstract: In this memo, we analyze the results of the audit of the AIPS++, and of evaluations of GILDAS and MIRIAD packages for compliance with the ALMA Offline Data Processing Requirements. These evaluations/audit show that about 2/3 of the SSR Requirements are fulfilled by each data reduction package, and almost 90% are fulfilled if we use existing software from all three packages.
Download: [ compressed PS file] or [ PDF file ].
2003 - 2
Evaluation of the GILDAS Package for ALMA Off-line Data Processing
Authors: F. Gueth (IRAM Grenoble), S. Guilloteau (ESO/IRAM Grenoble), R. Lucas (IRAM Grenoble), J. Pety (Obs. de Paris/IRAM Grenoble), M. Wright (RAL, U.C. Berkeley)
Keywords: Requirements, Offline, Software, Science, Calibration
Abstract: This memo presents the evaluation of the GILDAS package for compliance with the ALMA off-line data processing requirements (ALMA-SW Memo 18). This evaluation follows exactly the same template that was used for the AIPS++ audit.
Download: [ compressed PS file] or [ PDF file ].
2003 - 1
Evaluation of the MIRIAD Package for ALMA Off-line Data Processing
Authors: M. Wright (RAL, U.C. Berkeley), P. Teuben (U. Maryland), J. Pety (Obs. de Paris/IRAM Grenoble)
Keywords: Requirements, Offline, Software, Science, Calibration
Abstract: This memo presents an evaluation of the MIRIAD package for compliance with the ALMA off-line data processing requirements (ALMA-SW Memo 18). This evaluation follows exactly the same template that was used for the AIPS++ audit.
Download: [ compressed PS file] or [ PDF file ].





2001 - 1
A Calibration Scheme for the IF Polarimeter using the Coherence Matrix Formulation
Author:
H. Wiesemeyer (IRAM Grenoble)
Keywords: polarimetry, calibration, Stokes parameters, IF polarimeter, Jomes matrices, coherence matrix
Abstract: A calibration scheme for the IF polarimeter at the MRT is worked out using Jones matrices and the quantum-mechanical density operator (the
coherence matrix in classical theory). It is shown that the proposed calculus combines the advantages of Jones calculus and Mueller matrices.
Download:
[ compressed PS file ] or [ PDF file ]
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