Time management in test and flight operations: Accessing and analyzing time discontinued data

Abstract

Viewed under most circumstances, linear and continuous time information is needed to characterize data and perform data analysis. When time information is non-sequential, non-linear, or outright missing from a dataset, one has a difficult time recreating the original experiment's conditions necessary to analyze and interpret science or engineering data. The reasons for time discontinuities in stored data cannot be realistically overcome. During Integration and Testing (I&T), time information is naturally fragmented by the different test configurations making it difficult at times to coordinate test simulation with wall clock time; moreover, anomalies affect both pre and post launch time information data resulting in datasets with similar timestamps, often referenced to a common basetime epoch to which a processor regresses to by default. As a result, timestamp data collected on board can jump time spans unrealistically, or be missing completely from several packet production cycles. To cope with time discontinuities in the collected data, the question becomes how one can closely recreate the respective event's continuous timeline so that the data can be interpreted with the highest accuracy possible. We present several work example cases and solutions, with their advantages and disadvantages, based on the knowledge acquired with the LASP Mission Operations and Data Systems Group (MO&DS). We define the several contexts presented given the different types of spacecraft, payloads, and systems used. We also discuss database and data processing software management constraints as applied to time data information management relevant to space operations and telemetry data storage - an effort that can be overlooked during proposal phases of a mission. Finally, we propose an approach to a time data continuity management standard for space operations I&T and Flight conditions. The goal is to outline the minimum requirements baseline for a time information data management standard that would significantly reduce the effort to manage time discontinuities. The overall discussion and solutions consider several current models and tools, such as the SPICE Toolkit, developed by the Navigation and Ancillary Information Facility (NAIF) at NASA's JPL, and used for mission planning as well as ancillary and time information data management. We also consider, in the end, the likely inevitable human in the loop with the related implications, when it comes to the complexity of time information management.