Software cost estimation for the LADEE mission

Abstract

The purpose of the Lunar Atmosphere Dust Environment Explorer (LADEE) mission was to measure the density, composition and time variability of the lunar dust environment. The ground-support and onboard flight software for the mission was developed using a “Model-Based Software” methodology. In this technique, models of the spacecraft and flight software are developed in a graphical dynamics modeling package. Flight Software requirements are prototyped and refined using the simulated models. After the model is shown to work as desired in this simulation framework, C-code software is automatically generated from the models. The auto-generated code is then integrated with the Core Flight Executive and Core Flight Services (cFE/cFS) packages, VxWorks and appropriate board support packages. The generated software is then tested in real time Processor-in-the-Loop and Hardware-in-the-Loop test beds. Software cost estimation for the mission was performed 3 ways: 1) Extrapolated from development of a earth-based prototype hover-test vehicle, 2) Estimated through the Goddard Space Flight Center “mission design center” 3) Through the use of COCOMO based estimation spreadsheets. In this paper, we will discuss the characteristics of each of the cost estimation methods, and how they were tuned for a model-based development effort rather than a traditional effort. The estimates are also compared with actual costing and trend data for the LADEE Flight Software effort.