A preliminary list of Radar headers for comments and suggestions

Data Acquisition Modes

There are several data acquisition modes, some of which may be hidden. For example, for short Round Trip Times, it is may be better to put the T/R times in the per-record rather than per-file header.

File Headers for Arecibo Radar Data

I include the headers from various old (NURAD-era) files, and anything else that seems reasonable. There were various hardware-specific pieces of information in the old system (frequencies of specific LOs) that will likely be different now. Capital letters generally indicate that an old NURAD or MAIN header exists

1996 December 5: I've gone through this and tried to consider how it fits into the AO header scheme, as described in Phil Perrilat's .h files. These will be marked NAO (new AO) for now. Phil has libraries to read and write some / most of these.

1996 December 13: Don insists that the format must be one continuous data stream, i.e., no separate files for transmit and receive (which was what I suggested), and with the ephemerides interspersed. Perhaps this could be a "group"? with records ETRRRRRR ETRRRRRR, or something like that. He also wants multiple copies of the xmit and ephemeris information in case of tape problems.

Head-of-File Header Information

Magic Number

Some sort of "magic number" to identify this an AO raw data file. (NAO: HDRAO_STD.hdrMarker / HDRAO_IS_HDR(phdr))

Header ID

Version number for header so that, in principle, you can determine the format from a database. This may not be necessary if it's keyword-value. NAO: Each piece of the header (main, RI, experiment) has a version number, which means you have to be careful to start, but maintainance should be fairly easy. (HDR_XXX_VERSION, HDRAO_STD.version)

TapeID

Tape ID number (The AO# if possible, like a tape label)

File ID

File sequence number. This is in the format YYDDD.NNNNN, where YY is the last two digits of the year, DDD is the DOY, and NNNNN increments from one each day. There was a motion at a RA meeting to make the first 5 digits be MJD, but it was quashed. NAO: HDRAO_STD.scanNumber

observer ID

Operator ID

The observer and operator ID could just be an 80 character field for "who was there" The "cognizant observer" and/or "cognizant operator" should be here.

program ID/Experiment Number

Time allocation ID (may be useful to document observation or lack thereof for various purposes) NAO: Is this HDRAO_STD.expNumber?

Configuration File Date

Date when setup file was generated, or possibly submitted to the system (or both, better yet). NAO: Does this go in the sec.inp? Or where?

run number

data file sequence number

Date

UT date of experiment start NAO: HDRAO_STD.date, HDRAO_STD.time

JDate

Julian date of experiment start

Is Radar

This is an AO radar experiment (AO transmitter is used), and uses the XYZ transmitter. NAO: HDRAO_STD.expNumber?

Time-start

UT Time of receive start for first pulse (used to be AST?) NAO: in decoder header

Exposure time

Length of time to exposure end

Transmit start

UT Time of transmit start for first pulse

Transmit time

length of transmit time

Transmitter Location

Which transmitter

Transmit Ephemeris

Transmit coords and Doppler

Transmit Dropouts

Times and reasons for transmit failure

BANDWD

Receiver Bandwidth NAO: HDRAO_DECODER

XFrequency

Base Transmit Frequency, either actual or (center or first?) for frequency hopping.

RFrequency

Base Receive Frequency

NCHAN

Number of channels (what does this mean in the current scheme?)

NCPOL

Number of polarizations. NAO: HDRAO_DECODER

Circular

Circular or linear polarization?

IPP

Acquisition time for one cycle. This is probably a code length (for ranging), or a convenient interval for FT for CW. In the old system, frequency-hopping arranged to have an integral number of these, plus some slop on each side, in each "hop".

NDATAP

Samples * Channels / IPP

Code Length

Code length in bauds. 0 for CW, -N for (2^N)-1 long code NAO: HDRAO_DECODER

Code ID

Some sort of identification for the code (0 for CW). NAO: HDRAO_DECODER

Code start position

Position in code when transmitter started. -1 for "unknown"?? NAO: HDRAO_DECODER

Baud Length

Baud length in ns. NAO: HDRAO_DECODER

Sample Gate Time

Sample time in ns (probably 1 or 2 times Baud Length) Old system used both this and NSPB (Number of samples per baud)

Gate Delay

Time between "tick" and sample start.

Sampler samples per baud

samples per baud, probably 1 or 2. NAO: HDRAO_DECODER

Output samples per baud

Samples ber baud output from device: the decoder can combine 2 samples per baud except at 50ns. NAO: HDRAO_DECODER

NFREQ

Number of different frequencies for frequency hopping. NAO: HDRAO_

FRSTEP

Delta-frequency for hopping;

FRTIME

Time for each frequency

RESTR

Restart flag (so the system knows to resume an in-progress experiment)

Ephemeris Delay

Time interval between start of data taking and expected arrival of first echo so that the turnon is clear.

IDL

IDL In decnew. What is it?

RIST

"Time from marker to data start" Time from tick to code-start (measured?)

Ephemeris

The complete ephemeris, at 1 minute intervals. Was that ever too long? Save XDoppler, RDoppler, RTT, RA2000, Dec2000, Az, El

Ephemeris Setup

How to regenerate the ephemeris. If it's a two-body ephemeris for the short term, this can just be the elements. In that case, the elements ought to have a version, like MPC number, or something like that.

Interpolation Methods

The ephemeris is sub-interpolated. The current method is the 4th order polynomial generated using 5 minutes of ephemeris and Pascal's triangle (for Doppler), and linear interpolation (I assume) for RTT and AzEl.

Cals

Various things for cals??

Power

Transmitter power at various times

Transmitter configuration

What transmitter mode? Transmitter status.

Complex/Real Data

Direct-sampled data records are written as complex / real numbers

FT Data

FT's of direct-sampled records are written

Frequency direction

Direction of increasing frequency, or, whether a high-side (inverting) or low-side (non-inverting) LO is used.

Decoded Data

Decoded data are written

Decoded Samples Retained

Which delay bins are saved from decoded data?

Sampled Bits/sample

Bits per sample

Samples/word

Samples per written 32 bit word??

Interlace

How samples are interleaved: IQIQ or IIQQ or I*recl Q*recl; LRLR or L*recl R*recl; which samples are in which positions? Should be sample-wise, as word packing is separate

Per-Record Header Information

I assume each transmit cycle gets at least one record, thought I suppose it's conceivable that there would be occasions not to, particularly since the fastest likely data rates for asteroids are the ones with the shortest RTTs.

Record Number

Record Number in file

Record Length

Record length

Frequency Number

Which transmitter frequency for frequency-hopping. May also be relevant for multiple receiving bands.

Transmit start

Time of transmit start for this pulse

Transmit time

length of transmit time for this pulse (Could be Transmit Stop instead)

Recv start

Time of receive start for this pulse

receive time

length of receive for this pulse (could be receive stop instead)

RTT

RTT for this observation

Doppler

Avg Doppler for this observation? Or is it better to just go with the ephemeris?

Attenuators, gains, levels

These need to be recorded.

Other Observatories

For comparison, look at the Green Bank Header (a FITS BINTABLE) and the VLBA Header.

Unfortunately, Also relevant is the Definition of FITS. Yes, in 1996, there are still people using two digits for the year, and they is us.

Well, in September 1997, a four-digit year format is close to being adopted: Use DATE-OBS='2097-10-31' to represent 2097 October 31. DATE-OBS='31/10/97' will always mean 1997 October 31.

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Last update: 1997 September 15