FRSR Data Description

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Remote Measurements & Research Company 214 Euclid Av. Seattle WA 98122 michael@rmrco.com October 8, 2017 frsr data description.

1 Remote Measurements & Research Company 214 Euclid Av. Seattle WA October 8, 2017 frsr data description.pdf FRSR Data Description This document is a review of the data stream from the Fast-Rotating Shadowband Radiometer (FRSR) during normal operation. A basic description of the FRSR system and a description of the installation are provided in [1] and [2] below. A knowledge of these will help the reader in reading this description of the data. Background documents [1] Basic description [2] Installation & Operation frsr_raw Instrument, hardware FRSR Z_frsr frsr_interp Program File InterpFrsrPacket daq_data_files Figure 1: Raw data processing. The ethernet stream is read by the program Z frsr. The FRSR output is RS232 at bps. The serial stream is converted to ethernet and ingested by the PC. Data Folder The data folder is arranged like the example here: FRSR main folder sw/ all DAQ software. data/ all data data_ t135210z/ data folder created at time frsr_interp_ txt interpreted data for this day. frsr_raw_ txt raw data for this day su_ t135210z.txt setup file info.txt Folders like data_ t135210z/ 1, are created each time the command Startfrsr is called. (The Startfrsr evokes the program PrepareForRun which creates the folder and copies the current version of su.txt, with timestamp into it.) During data collection, the program Z_frsr recognizes incoming raw packets and writes them to a raw data file named frsr_raw_yymmdd.txt, where yymmdd = year,month,day. Example = frsr_raw_ txt. The raw packets are also input to a Perl program called InterpFrsrPacket which decodes the psuedo ascii and writes the result to frsr interp yymmdd.txt. New files are written each day. time. 1 The ISO timestamp in the form yyyymmddthhmmssz is used in naming many files. The timezone Z indicates we are using UTC

2 2 Background Figure 2: MFR passbands. The top of the atmosphere (TOA) and ground level radiation curves define the atmospheric transmittance, represented by the atmospheric optical depth (AOD), τ. Radiation in an open silicon cell and in six 10-nm wavebands (415,500,615,680,870,940 nm) are measured. The corresponding seven analog channels, are recorded by the FRSR. Figure 3: How the sweep is partitioned. As the shadowband rotates around the MFR head it makes different measurements at different millisecs from the nadir point, N. The time for a complete rotation is determined from consecutive N s. At the time the shadowband is at the first horizon the tilt (pitch and roll) are measured and the heater is turned off. Then, while the shadowband covers the upper hemisphere the analog-to-digital converter (ADC) takes 250 samples for each of the seven channels. At the second horizon, a second tilt is measured and, if necessary, the heater is turned on. From points P2 to N the FRSR microprocessor must determine sweep configuration, read the GPS, prepare the packets and transmit to the DAQ. Sweep block averaging bins The 250 sweep measurements are converted into 23 bin averages (below), b ij, i = 1..., 23, j = The 23 bins and the number of points in each bin are shown. Bin 12 is the minimum (shadow) point. Any bins that are entirely below the horizon are set to zero. Bin # N avg Min

3 3 Figure 4: A clear sky sweep. Shown are all 250 samples of one of the seven MFR channels. The y-axis is the measured millivolts and the x-axis is the sample count where 0 is the minimum voltage measured. In order to reduce noise and to reduce the size of the data transfer, the 250 samples are bin averaged into 23 bins which are shown by the open circles. Bin 12 is always the minimum value. Psuedo-ascii compression The psuedo-ascii coding was first developed by NOAA in order to increased data throughput in the GOES satellite system. Only ASCII data was permitted and so the psuedo-ascii compression allowed each six bits of a binary file to be written as a printable character. The resulting file is ascii text and about half the size of the file if numbers were printed as integers. [1] HIGH-SHADOW 462 CHARACTERS $FSR03,H,29.6,<<$GPRMC,212651,A, ,N, ,W,000.0,000.0,270517,>>, 83B3,\P[P,hPiP,W7Y9 7K7k608S9,C83:<858I7 8G:,=3T1,V7S7O7I7J7K7E7E7D7X4g0^0c082k6S7Z7 _7d7e7l718=8,O9H999G98919l8m8j8O632d1j1m2b7P9<9:9@9E9N9V9n9,X7U7L7F7R7A7B7A7e48 1o0m0=237L7N7R7U7Z7\7f7k7;8,K7I7G7F7<7:7E777B6S1i0[0k0D5A7I7S7P7V7V7\7 7k7,i6j6c6a6^ 6]6\6Y6[6Z63500^0V0G1e5d6m <7I7,0848e7g7f778e7b7Y7I3Z000T0K3b788<8O8F8I8K8]8\ 8,N9I9=9P9?9?989=9A95601^0d0I2F8R9n9 9j9d90:6:A:,*2E [2] NO-SHADOW, TRANSITION OR LOW MODE 133 CHARACTERS $FSR03,H,31.2,<<$GPRMC,125611,A, ,N, ,W,000.0,239.4,280517,>>,83B3, bpcp,7q:q, 1Y1^1S1X1=2N1,\1R1N1H1X1>2I1, 0T1,*68 Above are two examples of FRSR raw output. Packets are defined by the header, $FRSR, and the checksum, *cc, where cc is a hex checksum. The first character after the header is the mode which can be [H]igh when the global irradiance is above a set threshold, [T]ransition occurs during a ten-minute period after the radiation falls below the threshold and [L]ow mode occurs after the transition period. frsr_raw files are simply the packets as received.

4 4 Unpacked packet The file InterpFrsrPacket takes a psuedo-ascii FRSR packet and decodes it into a readable format. H, 2017,05,27,21,26,51, , , 0.0, 0.0, 0.0, 1.0, 0.92, 0.91, 1.04, 1.05, 20.5, Description These three lines are always output. md yyyy MM dd hh mm ss lat lon sog cog T1 T2 pi1 pi2 ro1 ro2 shad shlim H, 2017,05,27,21,26,51, , , 0.0, 0.0, 26.5, 27.4, 0.92, 0.91, 1.04, 1.05, 20.5, 10.0 Globals chan g g example: g13 is global value, first horizon, channel 3 = bin bin bin bin bin bin bin example b615 is the bin average for channel 6, bin15 = 498. When in H mode and shad shlim, the sweeps are output. Seven channels and 23 bin averages. Bin 12 is the shadow value.

5 5 md yyyy MM dd hh mm ss lat lon sog cog T1 T2 pi1 pi2 ro1 ro2 shad shlim gij bij Mode. The mode is either [H]igh, [T]ransition, or [L]ow. year. month. day of month. hour of day. minute of the hour. second of the minute. latitude from GPS, floating point, N+, S-. longitude from GPS, E+, W-. speed over ground from GPS, kts. course over ground from GPS, degt. MFR, temperature inside the cube, degc MFR temperature outside the cube, degc Pitch when shadowband was at horizon 1, degrees, +bow up. Pitch when shadowband was at horizon 2, degrees, +bow up. Roll when shadowband was at horizon 1, degrees, +port up. Roll when shadowband was at horizon 2, degrees, +port up. Shadow for the sweep. shadow = (edge-shadow)/adcnoise. Shadow ratio limit defines a good shadow. Global voltage, i = [1, 2] is the horizon and j = [1 7] is the channel. Millivolts. Bin average, i = [1 7] is the channel and j = [01 23] is the bin number. Millivolts.

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