Tropical Rainfall Measuring Mission Satellite Research Articles

2.1.2 Spacecraft Performance Requirements Tracking and Verification for the Tropical Rainfall Measuring Mission

AbstractThe Tropical Rainfall Measuring Mission (TRMM) is a joint United States and Japan observatory program that will conduct systematic measurements of tropical rainfall required for major strides in weather and climatic research. The TRMM satellite is scheduled for launch in August 1997 aboard a Japanese H‐II rocket. Although significantly along in the requirements development process, a decision was made in June 1994 to initiate an automated computer‐based requirements tracking and verification system. The automated computer‐based system facilitated the task of insuring all top‐level system requirements were properly addressed in subsystem level documentation and subsequently verified through uniquely identifiable verification activities.The Requirements Tracking System (RTS), a PARADOX for Windows based relational data base tool for managing project requirements, was chosen due to its low cost, flexibility, and favorable use on other Goddard Space Flight Center (GSFC) projects. Considerable time was invested creating the initial data base. The four step process involved electronically importing existing requirements specifications, isolating and classifying each requirement, allocating top‐level requirements to subsystems, and establishing the child‐parent relationship between each requirement. The completed data base helped to identify top‐level requirements without corresponding subsystem requirements (childless parents) and subsystem requirements without corresponding parents (orphans). Each requirement was addressed individually to insure total traceability of TRMM project requirements.In order to insure that each requirement developed for the in‐house designed and built TRMM satellite was addressed by subsystem designers, spacecraft performance requirements verification matrices were developed. At the subsystem level, specific test procedures, analyses, and demonstration/inspection activities were tied to each subsystem requirement. Subsystem level verification activities were then used to assess the design implementation(s) selected for top‐level space segment requirements. The verification matrices will be used during upcoming verification activities to insure compliance with requirements as well as analyze potential implications of non‐compliance or test failure.

A Proposed Tropical Rainfall Measuring Mission (TRMM) Satellite

The proposed Tropical Rainfall Measuring Mission (TRMM) satellite (presently in its third year of planning), is described. The TRMM satellite, planned for an operational duration of at least three years beginning in the mid-1990s, is intended to obtain high-quality measurements of tropical precipitation by means of information derived from a quantitative spaceborne radar, a multichannel passive microwave radiometer, and an AVHRR. The satellite's orbit will be low-altitude (320 km), for high resolution, and low-inclination (30 to 35 deg), for making it possible to visit each sampling area twice a day. Radar and passive microwave algorithms and rain-retrieval algorithms to be used in precipitation measurements are discussed together with cloud dynamical models designed to test these algorithms.