ALOS Data Users Handbook

Section 3 Outline of ALOS Satellite SystemTable 3.4-4 Fixed Bias of PRISM Imaging Time DataFixed Bias (ΔT delay ) 1.714 (μsec) (a) - (b)(a) Processing delay at DET/ASP 2.214 (μsec) Completion of transmission from Sync(b) Processing delay at ELU 0.500 (μsec) Taking of time data from SyncTable 3.4-5 Indefinite Error of PRISM Imaging Time DataIndefinite Error δT 3σo-p16.5 (μsec)(3σp-p)The high-order time information (GPS week 16 bits + GPS second high-order 11 bits) is not included in the timedata attached to the observation signal. The information can be extracted from PCD data in the PRISM missiontelemetry which is multiplexed to the observation signal at ALOS/MDHS, and transmitted to the ground.0.370 msec(20720clocks@56MHz)LineSync signal(ELU to ASP)64 clock(nominal)Enable signal(ASP to ELU)31 clock(nominal)213 clock64 clock(nominal)0.5μsec1.5 clock(nominal)1.5 clock(nominal)56MHz clock signal(ASP to ELU)Observation signal(8 bit)(ASP to ELU)D n1071(nsec)Count up of 19-bit self-running counter by1MPPS reference signal0.3611(msec)+/-142(nsec)t n(a) Taking of 1PPS reference signal(GPS time): T GPS (40bit)(b) Reset of ELU self-runningcounter (19bit)Taking of timedata: T nCompletion of transmissionfrom CCD element to transferregisterCompletion of transmissionof observation signal fromASP to ELUWriting to output buffer of ELULine counterTime data: T nADS data: ADS nObservation signal: D nTaking of ADSdata: ADS nLow-order 13 bits of GPS time (T GPS )(0 to 8,191sec; LSB=1sec)High-order 16 bits of self-running counter(0 to approx. 1sec; LSB=16μsec)Figure 3.4-8 Addition Sequence of Imaging TimePRI-ELU takes all PCD that consists of the 1PPS reference time and auxiliary data each second, and outputs allof them as mission telemetry each second. To confirm line loss of imaging in ground processing, a 3-bit linecounter is added to the image data along with the imaging time.The relation between imaging time data and real imaging is as follows:3-36