NASA Ocean Color

ocssw V2022

 #!/usr/bin/env python3
 from telemetry import ccsdspy
 from io import BytesIO
 from telemetry.timestamp import *
 from telemetry.PacketUtils import readFileHeader
  
 __version__ = '3.0.0_2024-02-26'
  
  
  
 def get_timestamp(all_packets, is_stime=True):
     '''
     Given a CCSDSPY packet list, get the start or end time
     from the packets
  
     PARAMETERS:
         all_packets : List of bytes
         is_stime : True for start time, False for end time 
  
     RETURNS:
         datetime
  
     '''
     # reading backwards or forward range object
     range_order = range(len(all_packets)) if is_stime else reversed(range(len(all_packets)))
  
     time = None
     for i in range_order:
         packet = all_packets[i]
         data = packet[6:]
         header = ccsdspy.utils.read_primary_headers(BytesIO(packet))
  
         for k, v in header.items():
             header[k] = v[0]  # remove outer array
  
         #check for invalid header
         if header['CCSDS_PACKET_LENGTH'] > 16378:
             continue  # go to next packet
  
         # check for truncated data
         if len(data) < header['CCSDS_PACKET_LENGTH'] + 1:
             break    # done with this file
  
         if (header['CCSDS_SECONDARY_FLAG'] == 1
             and data[0] > 112   # after  2017-07-18T05:49:15Z
             and data[0] < 192): # before 2060-01-28T16:50:35Z
             timestamp = readTimestamp(data)
             time = tai58_as_datetime(timestamp)
             break # only need the first valid time for forward and backwards reading
         
     return time.strftime('%Y-%m-%dT%H:%M:%S.%f')
  
  
  
 def l0info_hkt(args, fh, output):
     # procedure to get start and end times from PACE S-band HKT data file name
     print("Running l0info_hkt (version: %s) \n" % __version__)
     
     if args.verbose:
         print("Reading PACE S-band data file.")
  
     status = 104
     try:
         # read the CFE header and advance the reading pointer if it exists
         headerInfo = readFileHeader(fh)
  
         # if not a PACE file, raise exception
         if (headerInfo["SCID"] != b"PACE"):
             print('Not a valid PACE L0 file')
             status = 102 # invalid instrument 
             raise Exception
  
         # get all the packets
         all_packets = ccsdspy.utils.split_packet_bytes(fh, include_primary_header=True)
  
         # get the start and stop times 
         stime = get_timestamp(all_packets, True)
         etime = get_timestamp(all_packets, False)
  
         print("start_time=%s" % stime)
         print("stop_time=%s" % etime)
         
         if output:
             output.write("start_time=%s\n" % stime)
             output.write("stop_time=%s\n" % etime)
      
     except Exception as e:
         return status
  
  
     # status 0 if no issues
     return 0