Abstract
Estimating the size and amount of resources required to develop a large and complex software system is challenging. Early in a project lifecycle, requirements for the system may be immature and functionality defined only at a high level, yet resource profiles are necessary for appropriately funding, staffing, and developing a viable project plan. In addition, recommendations on key recurring questions related to software size and functionality (such as processor sizing, implementation phasing, allocations between the spacecraft and the ground, and possible downsizing/simplification opportunities) need to be established to aid in system design and efficient project planning. This paper presents the methodology and results of a bottom-up software size estimation and analysis study for NASA’s Orion crewed spacecraft flight software, based on functional software requirements developed during the pre-Preliminary Design Review (lifecycle) phase. Results of this study are used to independently assess contractor software size estimates, better understand envisioned functionality, and better manage resources and staffing. Data compiled in this study are also used to evaluate requirements generation process success as a basis to predict processor utilization, and to aid in software simplification, migration, and implementation phasing efforts.
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Abbreviations
- CEV:
-
Crew exploration vehicle
- COTS:
-
Commercial off-the-shelf
- CPU:
-
Central processing unit
- CSCI:
-
Computer software configuration item
- Hz:
-
Hertz
- ISS:
-
International space station
- MIPS:
-
Millions of instructions per second
- PDR:
-
Preliminary design review
- SEER-SEM:
-
System evaluation and estimation of resource—software estimation model
- SFM:
-
Software function manager
- SLOC:
-
Source lines of code
- SRS:
-
Software requirements specification
- SwRR:
-
Software requirements review
References
Galorath DD, Evans MW (2006) Software sizing, estimation, and risk management, Chap 3. Auerbach Publications, Boca Raton
Judas PA, Prokop LE (2012) A historical compilation of software and avionics metrics with applicability to NASA Orion spacecraft flight software sizing. Innov Syst Softw Eng (to be published)
Prokop LE, Hirsh RL, Pagan C (2012) Requirements-based execution time prediction of a partitioned real-time system using I/O and SLOC estimates. AIAA J (to be published)
Galorath DD (2008) SEER for software. Software project estimation and management Tool, Software Package, El Segundo
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Prokop, L.E. A requirements-based, bottom-up SLOC estimate and analysis of NASA’s Orion crew exploration vehicle spacecraft flight software. Innovations Syst Softw Eng 10, 93–101 (2014). https://doi.org/10.1007/s11334-012-0181-8
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DOI: https://doi.org/10.1007/s11334-012-0181-8