Data conduit protocol
From setiquest wiki
The page specifies the protocol of the data flow from the ATA to the cloud.
The data format corresponds to the exact header of the packets sent out by the channelizer, with a little more information appended onto the end.
This will be useful for developers ingesting this data into SonATA software running on their systems. The data could be fed into running instances of a DX, for example, just by removing the extra fields appended to the header.
Metadata for each packet is included in the header. The overhead is very minimal, and with all the information in the header, all data received by a developer is immediately identifiable. This makes using the data easy for developers.
Feedback to ATA is outside the scope of this protocol.
ATA to Amazon Data Format
This is a first attempt to define the structure of the data packets sent from a computer at the ATA to the AWS server, and ultimately to any listeners to the real-time data stream.
This specification does not attempt to define the client program that sends this data, nor does it attempt to define the server program that receives this data.
Assumptions
- The packets will be UDP.
- The values in the header shall be little endian.
- A packet of data is sent per packet received from the channelizer.
- The bandwidth will be sufficiently small to allow for easy transport over the limited internet speed available at the ATA.
Header and Data Specification
This header corresponds exactly to the header in the channelizer output, with some extra items added after the item "len". The items before "targetId" are defined in ATADataPacketHeader.h.
| Name | Size/Type | Explanation |
|---|---|---|
| group | 1 byte Unsigned byte |
The group of applications this type of packet belongs to. This is set to 0 at the ATA, the SETI data conduit will have a value of 1. |
| version | 1 byte Unsigned byte |
The version of this header. Not defined yet. Currently in SonATA the version is 0x01. |
| bitsPerSample | 1 byte Unsigned byte |
The number of bits per data sample. |
| binaryPoint | 1 byte Unsigned byte |
The implied fixed point position in the data. Normally 0. |
| order | 4 byte Unsigned integer |
An identifier showing the correct endian order. This should be 0xaabbccdd. |
| type | 1 byte Unsigned |
The type of the data. This is a bitfield:
|
| stream | 1 byte Unsigned |
If the data is single pol and the receiving software is expecting dual pol, the sending software can clone the first stream and set this field to a value of 1 to signify this is a clone. |
| polCode | 1 byte signed |
|
| hdrLen | 1 byte Unsigned |
The number of bytes in the header. |
| src | 4 bytes Unsigned int |
The source of the data:
|
| chan | 4 bytes Unsigned int |
The number of the channel this data came from in the channelizer. |
| seq | 4 bytes Unsigned int |
The sequence number of this packet |
| freq | 8 bytes Double precision |
The center frequency of the data. In MHz. |
| sampleRate | 8 bytes Double precision float |
(beamformer_bandwidth / fraction) / num_channelizer_channels |
| usableFraction | 4 bytes single precision float |
1.0 - beamformer_oversampling_pct |
| reserved | 4 bytes single precision float |
Reserved for future use |
| abdTime | 8 bytes Unsigned integer |
The time to the microsecond. UTC |
| flags | 4 bytes Unsigned int |
Value of 1 specifies the data is valid. |
| len | 4 bytes Unsigned int |
The number of bytes in the data. |
| targetId | 4 bytes unsigned integer |
The ID of the target. Information on this target should be easily obtainable from a database we provide an interface to in the AWS server. if the value is 65535 this signifies the source is just an RA/DEC, see the ra/dec values in the header. |
| bandwidth | 4 bytes Single precision float |
The bandwidth of the data in MHz. |
| az | 4 bytes Single precision float |
The AZ in degrees. |
| el | 4 bytes Single precision float |
The EL in degrees. |
| ra | 4 bytes Single precision float |
The RA in degrees. |
| dec | 4 bytes Single precision float |
The DEC in degrees. |
| data - unsigned char bytes. | ||
