/**********************************************************************/ /* RPWS_SCLK_SCET.FMT */ /* describes the structure of the spacecraft clock and spacecraft */ /* event time objects common to many Cassini RPWS archive files. */ /**********************************************************************/ OBJECT = COLUMN NAME = SCLK_SECOND DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 1 BYTES = 4 DESCRIPTION = "Spacecraft clock counter increments each second, beginning at approximately 1958-01-01T00:00:00Z." END_OBJECT = COLUMN OBJECT = COLUMN NAME = SCLK_PARTITION DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 5 BYTES = 1 VALID_MINIMUM = 0 VALID_MAXIMUM = 255 DESCRIPTION = "Spacecraft clock partition. A value of ZERO or ONE indicates the first partition (i.e. the spacecraft clock has not been reset)." END_OBJECT = COLUMN OBJECT = COLUMN NAME = SCLK_FINE DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 6 BYTES = 1 VALID_MINIMUM = 0 VALID_MAXIMUM = 255 DESCRIPTION = "Spacecraft clock modulo 256 counter increments 256 times per second. Since the RTI increments from 0 through 7 in this same interval, SCLK_FINE / 32 yields the RTI count. For RPWS, SCLK_FINE is maintained within the instrument to an accuracy of one RTI period. Time tags should occur only with the following values for SCLK_FINE : 0, 32, 64, 96, 128, 160, 192, and 224" END_OBJECT = COLUMN /**********************************************************************/ /* Note about archive product time-tags: */ /* We should be masking (removing) the lower 5 bits */ /* of SCLK_FINE prior to using SPICE to calculate SCET. */ /* */ /* RPWS time keeping occurs only with a resolution of the */ /* RTI period (ignore the sub-RTI counter we use with the */ /* WBR, the sub-RTI timing is included in the WBR minipacket). */ /* Both HRP and LRP use bit 0 to indicate a CDS clock */ /* update has not occurred in the last second (should always */ /* be clear on LRP and always set on HRP). */ /* Both LRP and HRP use bits 1-4 to hold a CDS packet count. */ /* LRP sets this counter to 0 while HRP start this count */ /* at 1, incrementing with each packet that is processed */ /* within any RTI period (in other words, HRP resets this */ /* counter to 1 when the RTI interrupt occurs). */ /* */ /* This has the side-effect that all SCLK values delivered by */ /* RPWS are unique. This also makes query by SCLK or SCET */ /* return data in an unambiguous order. */ /* */ /* BUT!!! It is necessary to clear bits 0-4 of the SCLK_FINE */ /* in order to get back to the intended (correct) time. */ /**********************************************************************/ OBJECT = COLUMN NAME = SCET_DAY DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 7 BYTES = 2 DESCRIPTION = "Spacecraft event time days since 1958-01-01T00:00:00Z" END_OBJECT = COLUMN OBJECT = COLUMN NAME = SCET_MILLISECOND DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 9 BYTES = 4 VALID_MINIMUM = 0 VALID_MAXIMUM = 86401999 DESCRIPTION = "Spacecraft event time millisecond of day allowing for up to two leap seconds." END_OBJECT = COLUMN /* END OF RPWS_SCLK_SCET.FMT */