The NGC 2903 ALFA Survey

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Notes on the first observing run: Nov 28-Dec 6, 2004

Observers:

Riccardo Giovanelli, Martha Haynes, Mary Putman, Barbara Catinella and Emmanuel Momjian

The ALFA Fixed Azimuth Drift Mode

A1963 uses an extension of the A1946 fixed azmith drift mode. See the A1946 memo which explains this mode in some detail.

Basic setup: SPECTRAL LINE OBSERVING

Setup	Setting	Comment
Center Freq	1417 MHz
LO tracking	None (Topocentric)	Best for rfi identification; unfortunately Doppler correction, although computed, not recorded in FITS file.
Bandwidth	12.5 MHz
Sampling	9 level auto	Best for sensitivity and rfi mitigation
# channels	2048/pol	(9 level reduces total # chans by half)
Drift length	480 seconds	The drift then lasts 8 minutes, and is set to begin when Beam 0 crosses RA(NGC2903) - 4 min. The CAL time is additional.
Cal mode	loopend or loopstart	All except Dec03 done in loop end. LIVEDATA requires loop start which Mary used on 12/03. However, then the actual drift start/stop times are not fixed, and this complicates true position checking vs. header positions (needed for continuum tests). Concerns raised about possible firing of cal on top of continuum source if fired at fixed point on sky throughout night. Mikael will add option for loopstart+loopend before run 2. Note that it takes 7 or 8 seconds beyond the end of the 480 sec drift to complete the 1 sec CalON plus 1 sec CalOFF. If we decide to select loopstart+loopend, that may require an additional overhead of 5-8 secs.
CIMA files	FixedAzdrift	Sources /home/lerner/fixedAZ2.tcl (executive) and /home/lerner/fixedAZ2_widget.tcl (gui)
	"Saved state"	a1963_hiline.gui

Basic setup: CONTINUUM BEAM MAP OBSERVING

Setup	Setting	Comment
Center Freq	1405 MHz
LO tracking	None (Topocentric)	Best for rfi identification; unfortunately Doppler correction, although computed, not recorded in FITS file.
Bandwidth	50 MHz
Sampling	9 level auto	Best for sensitivity and rfi mitigation
# channels	2048/pol	(9 level reduces total # chans by half)
Drift length	240 seconds	The drift then lasts 4 minutes, and is set to begin when Beam 0 crosses RA(calibrator) - 2 min. The CAL time is additional.
Cal mode	loopend	Better idea for position checks. See note above.
CIMA files	FixedAzdrift	Sources /home/lerner/fixedAZ2.tcl (executive) and /home/lerner/fixedAZ2_widget.tcl (gui)
	"Saved state"	a1963_beammaps.gui

This page created for the NGC2903 group by Martha Haynes and maintained by Barbara Catinella

Last modified: Mon Dec 6 14:47:46 AST 2004 by mph