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CCSDSPy provides an IO Interface for reading CCSDS data in Python. The CCSDS format is used for many NASA and ESA missions for low-level telemetry, and often contains tightly packed bits to reduce downlink requirements.

Install ccsdspy

To install ccsdspy from source, you can use

pip install ccsdspy


The CCSDS space packet protocol is a not a self-describing data format. Context for how to interpret the file’s bits must be provided. This information is typically available from the flight software documentation.

Fixed Length Packets

Fixed length packets are one type of packet defined in CCSDS. When provided with a description of data layout, ccsdspy.FixedLength will decode the fields automatically using highly efficient vectorized shifting and masking.

The result is returned as a dictionary, containing PacketField names as keys and values are each array of the interpreted data from each packet.

import ccsdspy
from ccsdspy import PacketField

pkt = ccsdspy.FixedLength([
     PacketField(name='SHCOARSE', data_type='uint', bit_length=32),
     PacketField(name='SHFINE',   data_type='uint', bit_length=20),
     PacketField(name='OPMODE',   data_type='uint', bit_length=3),
     PacketField(name='SPACER',   data_type='fill', bit_length=1),
     PacketField(name='VOLTAGE',  data_type='int',  bit_length=8),

result = pkt.load('MyCCSDS.bin')

Splitting Mixed Streams by APID

Often, CCSDS data will arrive from external sources into software systems in a single file with multiple APIDs. Splitting a mixed file or stream of bytes by APID so they can be used with the ccsdspy.FixedLength class can be done through the API or with the module command line interface.

from ccsdspy.utils import split_by_apid

with open('mixed_file.tlm', 'rb') as mixed_file):
    # dictionary mapping integer apid to BytesIO
    stream_by_apid = split_by_apid(mixed_file)
$ python -m ccsdspy split mixed_file.tlm
Parsing done!
Writing ./apid00132.tlm...
Writing ./apid00134.tlm...
Writing ./apid00258.tlm...
Writing ./apid00384.tlm...
Writing ./apid00385.tlm...
Writing ./apid00386.tlm...
Writing ./apid00387.tlm...

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