ICESat-2-SIPS-SPEC-0150 Software Version 004
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Table of Contents
ABSTRACT ........................................................................................................................................................................... 2
PREFACE .............................................................................................................................................................................. 3
LIST OF OPEN TBDS/TBRS ................................................................................................................................................ 4
LIST OF FIGURES ............................................................................................................................................................... 8
LIST OF TABLES ................................................................................................................................................................. 9
ACRONYMS AND TERMINOLOGY ................................................................................................................................ 11
1 INTRODUCTION ....................................................................................................................................................... 13
1.1 BACKGROUND ................................................................................................................................................................ 13
1.2 TERMINOLOGY, NOTATION, AND CONVENTIONS ............................................................................................................ 15
1.3 DESCRIPTION OF RELEVANT HARDWARE INTERACTIONS ............................................................................................... 17
1.4 INSTRUMENT DATA ........................................................................................................................................................ 25
1.4.1 Data Products ........................................................................................................................................................... 25
1.5 ATL02 SPECIFIC INFORMATION ..................................................................................................................................... 26
1.5.1 Knowledge of Instrument Configuration ................................................................................................................... 26
1.5.2 Control File & Overrides .......................................................................................................................................... 28
1.5.3 Relevant Calibrations ................................................................................................................................................ 28
1.5.4 General Data QA Philosophy .................................................................................................................................... 29
2 TIME OF DAY (TOD) CALCULATION ................................................................................................................... 30
2.1 CLOCKS AND TIMING RELATIONSHIPS ............................................................................................................................ 30
2.2 GROUND RULES & ASSUMPTIONS .................................................................................................................................. 31
2.3 VARIABLE DEFINITIONS AND NOTATION SYNTAX .......................................................................................................... 31
2.4 ESTABLISHING THE USO RULER CLOCK SCALE FACTOR ............................................................................................... 33
2.5 CALCULATION OF EVENT TIME OF DAY ......................................................................................................................... 34
2.5.1 Constructing AMET Counter Values ......................................................................................................................... 35
2.5.2 Determination of GPS Time of First T0 in Major Frame .......................................................................................... 36
2.5.3 Determining Effective Shot (T0) Count within Major Frame .................................................................................... 37
2.5.4 Calculation of GPS Time at T0 of Shot ..................................................................................................................... 38
2.5.5 Calculation of GPS Time of Leading Lower of Shot and Delta Time ........................................................................ 38
2.5.6 An Alternative View: Calculation of GPS Time of Leading Lower of Shot Expressed in AMET .............................. 39
2.5.7 Time Alignment of PCE Data .................................................................................................................................... 39
2.6 DEALING WITH MISSING DATA ...................................................................................................................................... 40
2.7 DATA QUALITY MONITORING ........................................................................................................................................ 41
2.7.1 Quality Check of TOD Calculation Inputs ................................................................................................................ 41
2.7.2 Confirmation of TOD Calculations and Data Alignment .......................................................................................... 42
2.7.3 Data Screening Mechanisms & Associated Responses ............................................................................................. 43
2.8 DATA PRODUCTS ............................................................................................................................................................ 43
3 TIME OF FLIGHT CALCULATION ........................................................................................................................ 45
3.1 GROUND RULES & ASSUMPTIONS .................................................................................................................................. 45
3.2 VARIABLE DEFINITIONS AND NOTATION SYNTAX .......................................................................................................... 46
3.3 MAPPING OF TRANSMIT AND RETURN EVENT INFORMATION ......................................................................................... 50
3.3.1 Laser Start Pulse Detector Channels ........................................................................................................................ 50
3.3.2 Photon Detector Channels ........................................................................................................................................ 50
3.4 CALCULATION OF START TIME ....................................................................................................................................... 51
3.4.1 Calculation of Leading Lower Start Event Coarse Time ........................................................................................... 52
3.4.2 Calculation of Other Element Start Event Coarse Time ........................................................................................... 52
3.4.3 Calculation of Transmit Event Fine Time ................................................................................................................. 52
3.4.4 Calculation of Precise Start Event Times .................................................................................................................. 55
3.4.5 Calculation of Precise Start Time & Overall Timing Uncertainty ............................................................................ 56
