Identifying the Observations: Who is Who ?

First, you can get more informations about the quality of your observations on the x999.note file. This file, written on the site by the astronomer on duty, contains a brief history of each observing run. Problems encountered, weather conditions, etc.. are mentionned. It is also convenient to have the observing procedure of your project: setup-x999.obs. In order to retrieve these files which are located on the Bure machines, ask your local contact.

Then before starting any calibration or editing, you must of course look at the data. A scanlist is an essential tool. Produce it using command LIST/OUPUT Filename and print the listing. But a summary list produced by LIST/SHORT/OUTPUT is usually enough because its gives all the fundamental steps of the observations:

1457_1459 EA21 3C454.3     P GAIN CO-ISO   w00w05e03    20-AUG-1994  -1.4_ -1.4
1460_1461 EA21 3C454.3     P GAIN CO-ISO   w00w05e03    20-AUG-1994  -1.2_ -1.2
1462_1464 EA21 3C454.3     P GAIN CO-ISO   w00w05e03    20-AUG-1994  -1.1_ -1.1
1465_1476 EA21 3C454.3     P CORR CO-ISO   w00w05e03    20-AUG-1994  -1.0_  -.9
1477_1479 EA21 3C84        P POIN CO-ISO   w00w05e03    20-AUG-1994  -5.2_ -5.2
1482_1482 EA21 0415+379    P FLUX CO-ISO   w00w05e03    20-AUG-1994  -5.9_ -5.9
1483_1485 EA21 0415+379    P CORR CO-ISO   w00w05e03    21-AUG-1994  -5.9_ -5.9
1486_1507 EA21 V773_TAU    O CORR CO-ISO   w00w05e03    21-AUG-1994  -5.8_ -5.4
1508_1513 EA21 0415+379    P CORR CO-ISO   w00w05e03    21-AUG-1994  -5.5_ -5.4
1514_1535 EA21 LKCA_3      O CORR CO-ISO   w00w05e03    21-AUG-1994  -5.3_ -5.0
...........
2162_2167 EA21 W3OH        P CORR CO-ISO   w00w05e03    21-AUG-1994  -2.0_ -2.0

In this short list, atmospheric calibration (named CALI) and passband calibration of intermediary frequency (named IFPB) are omited because they are systematically done before starting a cross-correlation CORR.

The scanlist written above contains the following informations:

	- First column: Scan number
	- Second column: Project name
	- Third column: Source name
	- Fourth column: Type of source (O=object, P=phase calibrator)
	- Fifth column: Type of observation
	- Sixth column: Line name
	- Seventh column: Configuration, i.e. antenna positions on the stations
	- Eighth column: Date
	- Nineth column: Hour angle interval.

The type of observations (column five) can be:

	GAIN: a cross-correlation in order to measure the sideband ratio
	CORR: a cross-correlation  
	FOCU: a simultaneous focus measurement on each antenna
	POIN: an interferometric pointing on all antennas
	FLUX: a flux measurement
	CALI: an atmospheric calibration (autocorelations on SKY and HOT load)
	IFPB: an IF passband calibration (done using the noise diode) 
	AUTO: an autocorrelation alone
	HOLO: an holography measurement

In the above example, the sequence of the observations (which is typical) was the following:

 - From 1457 to 1464: Receiver tuning and sideband gain measurements
 - From 1465 to 1476: Radio frequency passband calibration on 3C454.3  
 - From 1477 to 1479: Check of the pointing before starting integration
(after pointing, the focus may also be checked)
 - Scan 1483 : flux measurement of the calibrator.
 - From 1482 to 1485: First phase calibration
 - From 1486 to 1507: First cross-correlation on first source...
 - From 1508 to 2161: ... Project ...
 - From 2162 to 2167: cross-correlation on W3OH for flux calibration

Here the data to calibrate start with the scan 1465, i.e. the last GAIN measurement. The command SET SCAN 1485 * will permit to select the good scans. It is useful to calibrate simultaneously the data POIN, GAIN and CROSS. For example, the POIN on 3C84 will help for flux estimate. Cross-correlation on W3OH will be used as a check on the flux calibration because the flux of this HII region is well known between 80 and 115 GHz and not resolved on the shortest baselines (i.e. B < 100 m). CRL618 and MWC349 are also used for this purpose.