NASA maintains excellence in its spaceflight systems by utilizing rigorous engineering processes based on over 50 years of experience. The NASA systems engineering process for flight projects described in NPR 7120.5E was initially developed for major flight projects. The design and development of low-cost small satellite systems does not entail the financial and risk consequences traditionally associated with spaceflight projects. Consequently, an approach is offered to tailoring of the processes such that the small satellite missions will benefit from the engineering rigor without overly burdensome overhead. In this paper we will outline the approaches to tailoring the standard processes for these small missions and describe how it will be applied in a proposed small satellite mission

Belvin, Keith

Horan, Stephen

NASA Technical Reports Server

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Tailoring Systems Engineering Projects for Small Satellite Missions 
Stephen Horan and Keith Belvin 
NASA Langley Research Center 
Hampton, VA 23681 
UNITED STATES 
stephen.j.horan@nasa.gov / w.k.belvin@nasa.gov  
ABSTRACT  
NASA maintains excellence in its spaceflight systems by utilizing rigorous engineering processes based on over 
50 years of experience.  The NASA systems engineering process for flight projects described in NPR 7120.5E 
was initially developed for major flight projects.  The design and development of low-cost small satellite systems 
does not entail the financial and risk consequences traditionally associated with spaceflight projects. 
Consequently, an approach is offered to tailoring of the processes such that the small satellite missions will 
benefit from the engineering rigor without overly burdensome overhead.  In this paper we will outline the 
approaches to tailoring the standard processes for these small missions and describe how it will be applied in a 
proposed small satellite mission. 
1.0 INTRODUCTION 
The National Aeronautics and Space Administration (NASA) project management requirements for space flight 
projects is described in the NASA Procedural Requirements (NPR) document NPR 7120.5E [1]. This document 
outlines the necessary design reviews and project documentation required for flight projects conducted by the 
Agency.  The process prescribes design and development activities that depend upon the criticality of the 
mission type with those missions of highest criticality requiring the most extensive engineering rigor.  While the 
cost of applying all the processes of NPR 7120.5E is acceptable for human-rated missions or missions with 
significant national investment, the use of all the processes is often viewed as excessive for smaller, higher-risk 
mission designs.  With smaller missions often having a technology development emphasis, such as a 
microsatellite mission with short development time and short mission duration, mission designers question the 
NPR 7120.5E process even further.   
Small satellite missions frequently have mission life cycle costs and mission durations that are inconsistent with 
NPR 7120.5E requirements.  The engineering and flight project community at Langley Research Center (LaRC) 
has been working to develop a method to tailor the NPR 7120.5E processes to meet the needs of these smaller 
missions and still provide adequate oversight over mission design and execution [2].  As part of this activity, 
LaRC has defined project “Types” described in Figure 1 that take into account not only project costs, but also 
acceptable risk.  In this paper, we will look at the process used at LaRC to tailor the engineering and design 
activities to smaller missions; the Type A through Type C missions are not subject to this process. 
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Figure 1: NASA mission classification types from highest to lowest criticality [2]. 
2.0 TAILORING PROCESS 
It is NASA policy that all prescribed requirements of NPR 7120.5E are complied with unless relief is formally 
granted. Policy also recognizes that each program or project has unique aspects that must be accommodated to 
achieve mission success in an efficient and economical manner. Tailoring is the process used to adjust or seek 
relief from a prescribed requirement to meet the needs of a specific program or project. Tailoring is both an 
expected and accepted part of establishing proper requirements. The request for relief from a requirement 
includes the rationale, a risk evaluation, and reference to all material that provides the justification supporting 
acceptance.  
The shift in emphasis from large missions with long development cycles to small missions with rapid 
development cycles requires a shift in philosophy towards a “lean thinking” approach as recommended in [3]. 
This does not mean throwing out engineering processes but appropriately adapting them to the needs of the small 
mission environment.   
The tailoring process described herein attempts to balance the needs and scope of the smaller mission with the 
need for management oversight and adequate engineering discipline.  The process starts with the required steps 
in the NPR 7120.5E process and then suggests levels of compliance based on the mission type.  The levels of 
tailoring compliance are listed in Table 1.  While the tailoring tool has pre-suggested levels of compliance, none 
of these levels is automatically granted.  The project team will need to justify that the suggested compliance level 
for each project is appropriate and either engineering management or the project may require greater rigor if it is 
believed that the oversight level is necessary to assure project success.  
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Table 1: Basic tailoring definitions to apply to the process (based on [2]). 
Tailoring Term Meaning 
Blank/Empty Required Element for the project. 
Tailor Down Decrease the level of detail, formality, and rigor required based on the project’s size, 
complexity, and acceptable risk or the requirement may be captured/met by the 
fulfilment of another requirement. 
Tailor Out Seek relief from the requirement based on the project’s size, complexity, and acceptable 
risk. This may require a waiver. 
N/A Not applicable. The requirement is not relevant to the project type. 
Project Plan The intent of the requirement can be met and documented within the project plan. 
TOR The intent of the requirement can be documented within the project Terms of Reference. 
HQ/Center Used to identify the recommended level of decision authority. 
 
The suggested tailoring levels for the NPR 7120.5E processes are given in Table 2 and Table 3.  The technical 
and management work products are given first by mission type and then decision points and flight system 
management plans.  In both tables, if the entry under the mission type is blank, then that element is still required 
in the tailored process.  The non-blank entries show where a tailoring down or tailoring out of the usual 
requirement is suggested.  For some mission types, entries may even be suggested to be not applicable for the 
mission.  As mentioned above, these are suggested starting points but the final tailoring level must be justified by 
the project. 
The Key Decision Points (KDPs) typically found in a project have split responsibility between NASA 
Headquarters (HQ) and the implementing NASA Center rather than all being at HQ as in the larger projects.  
Because HQ funding is the usual initiator of a project, the initial Key Decision Point (KDP), A, remains with the 
responsible HQ Directorate for sponsoring the project.   
The NASA process requires several formal reviews tied to the KDPs and the flight process.  The tailoring of 
these review levels is shown in Table 4.  This includes the KDP reviews and the technical reviews found in a 
typical process.  In these reviews, the project peer reviews are required and not tailored down.  As with the 
technical work products, the tailoring of the reviews is suggested and negotiated with engineering management.  
A project may, for example option to hold a combined System Requirements Review and Mission Definition 
Review in place of tailoring out the MDR if engineering management and the project believe that this will lead 
to a higher probability of mission success. 
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Table 2: Suggested tailoring levels for the 7120 management processes [2]. 
Project Technical Products Type D Type E Type F 
1. Mission Concept Report Tailor Down Tailor Down Tailor Down 
2. System Level Requirements   Tailor Down 
3. Preliminary Design Report  Tailor Down Tailor Down 
4. Mission Operations Concept  Tailor Down Tailor Down 
5. Technology Readiness Assessment Tailor Out N/A N/A 
6. Missile System Pre-Launch Safety Package   N/A 
7. Detailed Design Report  Tailor Down Tailor Out 
8. As-Built Hardware and Software Documentation   Tailor Down 
9. Verification and Validation Report Tailor Down Tailor Down Tailor Down 
10. Operations Handbook  Tailor Down Tailor Out 
11. Orbital Debris Assessment  N/A N/A 
12. Mission Report Tailor Down Tailor Down Tailor Down 
Project Planning, Cost, and Schedule Products 
1. Work Assignment for next phase  Tailor Down Tailor Out 
2. Integrated Baseline Tailor Down Tailor Down Tailor Out 
3. Project Plan  Tailor Down Tailor Down 
4. CADRe Tailor Out N/A N/A 
5. Planetary Protection Plan  N/A N/A 
6. Nuclear Safety Launch Approval Plan  N/A N/A 
7. Business Case for Infrastructure N/A N/A N/A 
8. Range Safety Risk Management Plan  N/A N/A 
9. Systems Decommissioning/Disposal Plan  N/A N/A 
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Table 3: Suggested tailoring levels for the 7120 management processes (cont.) [2]. 
Key Decision Points (KDP) Type D Type E Type F 
KDP A HQ HQ HQ 
KDP B Center Center Center 
KDP C HQ HQ Center 
KDP D Center Center Center 
KDP E Center Center Center 
KDP F Center Center Center 
Project Planning, Cost, and Schedule Products 
1. Technical, Schedule, and Cost Control Plan Project Plan Project Plan Tailor Out 
2. Safety and Mission Assurance Plan  Tailor Down Tailor Out 
3. Risk Management Plan Project Plan Project Plan Tailor Out 
4. Acquisition Plan Project Plan Project Plan Tailor Out 
5. Technology Development Plan Project Plan Tailor Out Tailor Out 
6. Systems Engineering Management Plan Tailor Down Tailor Down Tailor Down 
7. Software Management Plan  Project Plan Tailor Down 
8. Review Plan Project Plan TOR Tailor Out 
9. Mission Operations Plan  Tailor Down Tailor Down 
10. Environmental Management Plan Project Plan Project Plan Tailor Down 
11. Logistics Plan Project Plan Review Material Tailor Out 
12. Science Data Management Plan Project Plan Project Plan Tailor Out 
13. Information and Configuration Management Plan Project Plan Project Plan Tailor Down 
14. Security Plan Project Plan Project Plan Tailor Down 
15. Export Control Plan Project Plan Project Plan Tailor Down 
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Table 4: Suggested tailoring of project technical reviews [2]. 
Technical Review Type D Type E Type F 
LaRC 60-day review    
Mission Concept Review Tailor Down Tailor Down Tailor Down 
System Requirements Review Tailor Down Tailor Down Tailor Down 
Mission Definition Review Tailor Out Tailor Out Tailor Out 
System Definition Review N/A N/A N/A 
Preliminary Design Review  Tailor Down Tailor Out 
Critical Design Review  Tailor Down Tailor Out 
Production Readiness Review Tailor Out Tailor Out Tailor Out 
System Integration Review Tailor Down Tailor Out Tailor Out 
Test Readiness Review  Tailor Out Tailor Out 
System Acceptance Review  Tailor Down Tailor Out 
Operational Readiness Review Tailor Down Combine with 
FRR 
Combine with 
FRR 
Flight Readiness Review  Combine with 
ORR 
Combine with 
ORR 
Post-Launch Assessment Review Tailor Down N/A N/A 
Critical Event Readiness Review  N/A N/A 
Post-Flight Assessment Review N/A N/A N/A 
Decommissioning Review  N/A N/A 
Periodic Technical Review    
Technical Peer Reviews    
LaRC Lessons Learned Outbrief    
 
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3.0 APPLICATION EXAMPLE 
An example of applying this process is currently under development at LaRC where we are developing a 
scientific microsatellite project to advance modelling of cosmic ray effects.  A key component of the mission 
design is to instruct engineers, scientists, and support staff in the relevant design and review processes from NPR 
7120.5E but tailored for the mission context.   
The particular mission is called the Radiation Dosimetry Experiment (RaD-X) and it is competing as part of 
NASA’s Hands-On Project Experience (HOPE) program for early-career professionals.  RaD-X will fly a test 
mission on a high-altitude balloon to advance the space readiness of the technology involved in the science 
measurement and prepare the basic microsatellite infrastructure for an eventual space operation.  We are basing 
this process on a similar mission described in [4].  If NASA selects the mission for implementation, then the total 
mission cost will be approximately $2.25M, the mission total life cycle time will be 18 months, and the flight 
time will be one day.  This description fits with mission Type E or Type F, with the latter being the preferred 
classification.  The final determination will be negotiated as part of the selection in the proposal competition.   
As part of the mission development process, the RaD-X team needs to review the tailoring process outlined here 
and make suggestions to Center management for the approach that will apply to their mission.  This process will 
start with a 4-hour seminar on the tailoring approach conducted by the Chief Engineer’s office from the 
Engineering Directorate.  Because of the short development time, the instruction and starting the tailoring 
process will occur before NASA HQ announces the mission award.  Because one of the goals of the HOPE 
program is to provide early-career professionals experience with this type of smaller flight project that will give 
them the basis to understand the needs of larger missions, the tailoring process is one of the key educational 
points in the Rad-X development concept. 
4.0 CONCLUSION 
With continuing advances in technology, low cost small satellite systems could perform many of the missions 
currently achieved by large expensive spacecraft and instruments. To realize the full cost benefits of small 
spacecraft, the engineering and development processes must be appropriate to the risks (cost, technical and 
schedule).  The challenge is to use risk-informed decision making to select the technical and management 
processes such that the small satellite missions will benefit from the engineering rigor without overly 
burdensome overhead.   
Instead of developing new systems engineering processes from the bottoms-up, this paper suggests that tailoring 
of tried-and-true methods such as those found in NPR 7120.5E is a more rational approach.  Specific steps to 
tailoring of the “normal” systems engineering activities for small satellite missions are offered.  This tailoring 
approach is now being used for the proposed  Radiation Dosimetry Experiment (RaD-X) which is competing for 
selection as part of NASA’s Hands-On Project Experience (HOPE) program for early-career professionals.   
5.0 REFERENCES 
[1] National Aeronautics and Space Administration, NASA Space Flight Program and Project Management 
Requirements, NPR 7120.5E, August 14, 2012, 
http://nodis3.gsfc.nasa.gov/displayDir.cfm?t=NPR&c=7120&s=5E . 
[2] Langley Research Center, LaRC NPR7120.5D and NPR7123.1A Tailoring Guidelines (Baseline 1), 
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http://engineering.larc.nasa.gov/ . 
[3] Hunyadi, G., Ganley, J., Berenberg, L., and Henrikson, E., The AFRL/STP Nanosat-2 Mission on Delta IV 
Heavy: A Demonstration of Current Responsive Space Capabilities, Proc. 2005 IEEE Aerospace 
Conference (Paper #1169), Big Sky, MT, March 2005. 
[4] Horan, S., Hull, R., and Alvarez, L., Using a Balloon Flight for End-to-End Testing of a Nanosatellite 
Mission, Journ. Small Satellites, Vol. 1, No. 1, January 2012. 
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Tailoring Systems Engineering Projects for Small Satellite Missions

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