Data Format Descriptions

TBW

TBW consist of a time series of real valued data sampled at f_S (196 MHz) from all antennas in the array. The stand numbering is based on the input into the digital system rather than the stand number in the array. The data are divided into packets that contain either 400 samples (12-bit data) or 1200 samples (4-bit data) per stand per polarization.

Note

Fields are big endian

Byte(s)	Name	Description
0-3	Sync Word	0xDECODE5C
4-6	Frame Count	Frame number within capture
7	ID	Always zero
8-11	Second count	Always zero
12-13	TBW ID	Packed frame source ID
14-15	Unassigned	Always zero
16-23	Time tag	Time tag [1]
24-1223	Data	i4 or i12 data - [time,]

The packing on the TBW ID field is:

Bit(s)	Description
0-13	Stand
14	Sample Size (0 = 12-bit)
15	Is TBW? (1 = Yes)

Both the i4 and i12 versions of the data are stored as two’s complement integers.

TBN

TBN data is similar to TBW data, except that the data are complex and have a variable sample rate of up to 100 kHz. The data are divided into packets with 512 samples per stand per polarization.

Note

Fields are big endian

Byte(s)	Name	Description
0-3	Sync Word	0xDECODE5C
4-6	Frame Count	Always zero
7	ID	Always zero
8-11	Tuning Word	Tuning frequency [2]
12-13	TBN ID	Packed frame source ID
14-15	Gain	TBN gain used
16-23	Time tag	Time tag [1]
24-1047	Data	ci8 data - [time,]

The packing on the TBN ID field is:

Bit(s)	Description
0-13	Stand
14	Reserved
15	Is TBW? (1 = Yes)

ci8 is also known as “8+8-bit complex integer”.

DRX

DRX data consist of a time series of complex data sampled at f_S / Decimation Factor from the beamformer. The data are divided into packets of 4096 samples per beam per tuning per polarization.

Note

Fields are big endian

Byte(s)	Name	Description
0-3	Sync Word	0xDECODE5C
4-6	Frame Count	Always zero
7	ID	Packed frame source ID
8-11	Second Count	Always zero
12-13	Decimation Factor	Decimation factor of fS
14-15	Time Offset	Time correction to the time tag
16-23	Time tag	Time tag [1]
24-28	Flags	Always zero
29-31	Tuning Word	Tuning frequency [2]
32-4127	Data	ci4 data - [time,]

The packing on the ID field is:

Bit(s)	Description
0-2	Beam
3-5	Tuning
6	Always zero
7	Polarization

The ci4 aka “4+4-bit complex integer” data are stored as two’s complement integers with the real part stored in the first four bits of the byte.

DR Spectrometer

DR Spectrometer data contain DRX data that has been transformed to the Fourier domain, converted to power, and integrated on-the-fly by the data recorder. The format allows for variable integration times, channel counts, and polarization products to be stored.

Byte(s)	Name	Description
0-3	Magic Word 1	0xC0DEC0DE
4-11	Time tag	Time tag of first frame [1]
12-13	Time offset	Time correction to the time tag
14-15	Decimation Factor	Decimation factor of fS
16-23	Tuning Word[2]	Tuning frequencies [2] [3]
24-39	Fills[4]	Fill counts [4]
40-43	Errors[4]	Error flags [4]
44	Beam	Beam
45	Stokes Format	Polarization format code
46	Version	Packet format version
47	Flags	Bit flags
48-51	Nfreq	Transform length [5]
52-53	Nint	Integration count [5]
54-67	Sats[4]	Saturation counts [4]
68-71	Magic Word 2	0xED0CED0C
72-N	Data	float data - [pol,chan]

The Stokes Format is a bit field that defines what polarizations are included in the packet data. The fields are:

Value	Pol. Product
0x01	XX*
0x02	Real(XY*)
0x04	Imag(XY*)
0x08	YY*
0x10	I
0x20	Q
0x40	U
0x80	V

The data are stored as little endian float values.

TBF

TBF is similar to both TBW and TBN, but is a complex frequency domain product that contains blocks of 12 channels from all stands and polarizations. Each channel has a bandwidth of f_C (25 kHz) and there may be up to 132 different values of First Channel within a single recording. The stand ordering is based on the input into the digital system rather than the stand number in the array.

Note

Fields are big endian

Byte(s)	Name	Description
0-3	Sync Word	0xDECODE5C
4-6	Frame Count	Frame number within capture
7	ADP ID	Always one
8-11	Second Count	Always zero
12-13	First Channel	First channel in packet
14-15	Unassigned	Always zero
16-23	Time tag	Time tag [1]
24-6167	Data	ci4 data - [chan,stand,pol]

The ci4 aka “4+4-bit complex integer” data are stored as two’s complement integers with the real part stored in the first four bits of the byte.

COR

The COR format contains full polarization complex visibility data for 132 channels from a single baseline pair. Each channel has a bandwidth of f_C (25 kHz) and there may be up to six different contiguous values of First Channel within a single recording. The stand numbering for the baseline pair is based on the input into the digital system rather than the stand number in the array.

Note

Fields are big endian

Byte(s)	Name	Description
0-3	Sync Word	0xDECODE5C
4-6	Frame Count	Server ID
7	ADP ID	Always two
8-11	Second Count	Always zero
12-13	First Channel	First channel in packet
14-15	Gain	COR gain used
16-23	Time tag	Time tag [1]
24-27	Navg	Integration time in samples
28-29	Stand 1	First stand in baseline
30-31	Stand 2	Second stand in baseline
32-4255	Data	Complex<float> data - [chan,pol1,pol2]

The data are stored as little endian Complex<float> values.

[1] (1,2,3,4,5,6)

Time tags are expressed as uint64_t integers in units of ticks of a clock at f_S since the start of the UNIX epoch (1970 Jan 1 00:00:00 UTC)

[2] (1,2,3)

Tuning words are frequencies expressed as uint32_t integers in units of f_S / 2³² Hz

[3]

Ordering is [Tuning 1, Tuning 2]

[4] (1,2,3)

Ordering is [Tuning 1/pol 0, Tuning 2/pol 0, Tuning 1/pol 1, Tuning 2/pol 1]

[5] (1,2)

Valid values can be found at https://leo.phys.unm.edu/~lwa/astro/scheds/spec.html