Table 1: SPECTRAL_WINDOW: Spectral window description
SPECTRAL_WINDOW: Spectral window description

Name

Format

Units

Measure

Comments

Columns

Data description

NUM_CHAN

Int

s

# spectral channels

Data

NAME

String

Spectral window name

REF_FREQ

Double

Hz

FREQUENCY

The reference frequency

CHAN_FREQ

Double(NUM_CHAN)

Hz

FREQUENCY

Center frequencies for each channel in the data matrix

CHAN_WIDTH

Double(NUM_CHAN)

Hz

Channel width for each channel in the data matrix

MEAS_FREQ_REF

Int

Hz

FREQUENCY Measure ref.

EFFECTIVE_BW

Double(NUM_CHAN)

Hz

The effective noise bandwidth for each channel in the data matrix

RESOLUTION

Double(NUM_CHAN)

Hz

The effective spectral resolution for each channel in the data matrix

TOT_BANDWIDTH

Double

Hz

total bandwidth for this window

NET_SIDEBAND

Int

Net sideband

(BBC_NO) 

Int

Baseband converter no.

(BBC_SIDEBAND) 

Int

BBC sideband

IF_CONV_CHAIN

Int

The IF conversion chani

FREQ_GROUP

Int

Frequency group

FREQ_GROUP_NAME

String

Freq. group name

( DOPPLER_ID) 

Int

Doppler id.

( ASSOC_SPW_ID) 

Int(*)

Associated spw_id

(ASSOC_NATURE) 

String(*)

Nature of association

(BIT_SIZE)   

Int

Bit size

Flags

FLAG_ROW

Bool

The row flag


Notes:
NUM_CHAN
Number of spectral channels    
NAME
Spectral window name; user specified. Could this name be used to group spectral windows, e.g. for adjacent baseband, reserving the use of ASSOC_SPW_IDwith ASSOC_SPW_IDto associate data at different spectral/temporal resolutions? 
REF_FREQ
Reference frequency. A frequency representative of the spectral window, usually the sky frequency corresponding to the DC edge of the baseband. Used by the calibration system if a fixed scaling frequency is required or in algorithms to identify the observing band.  
CHAN_FREQ
Center frequencies for each channel in the data matrix. These can be frequency-dependent, to accommodate instruments such as acousto-optic spectrometers. Note that the channel frequencies may be inascending or descending frequency order.      
CHAN_WIDTH
Nominal channel width of each spectral channel. Although these can be derived from CHAN_FREQ  by differencing, it is more efficient to keep a separate reference to this information.    
MEAS_FREQ_REF
Frequency Measure reference for CHAN_FREQ . This allow a row-based reference for this column in order to optimize the Choice of the Measure reference when Doppler tracking is used. Modified only by the MS access code.    
EFFECTIVE_BW
Effective noise bandwidth of each spectral channel  
RESOLUTION
Effective spectral resolution of each channel  
NET_SIDEBAND
Net sideband for this spectral window
we propose: -1 NoSB, 0 DSB, 1 LSB, 2 USB, 3 2SB LSB, 4 2SB USB, 5 2SB LSB SBsep, 6 2SB USB SBsep.  
BBC_NO
Baseband converter number, if applicable.  
BBC_SIDEBAND
Baseband converter sideband, if applicable
IF_CONV_CHAIN
Identificaion of the electronic signal path for the case of multiple (simultaneous) IFs.
FREQ_GROUP
The frequency group to which the spectral window belongs. This is use to associate spectral windows from joint calibration purposes.
FREQ_GROUP_NAME
The frequency group name; user specified
DOPPLER_ID
Doppler identifier defining frame information for this spectral window.
ASSOC_SPW_ID
Associated spectral windows, which are related in some fashion (e.g. “channel-zero”).
ASSOC_NATURE
Nature of the association for ASSOC_SPW_ID; reserved keywords are CHANNEL-ZERO1 , EQUAL-FREQUENCY2 , SUBSET3 . N.B. For channel 0 a specific spectral window could be created where the number of channels would correspond to the number of basebands. This spectral window would be an associate in all the full resolution spectral windows. 
BIT_SIZE
16 or 32 bit signed integer to store the each of the complex component.
FLAG_ROW
True if the row does not contain valid data.