William O. Hughes and Anne M. McNelis

Glenn Research Center, Cleveland, Ohio

Statistical Analysis of a Large Sample Size 

Pyroshock Test Data Set Including 

Post Flight Data Assessment

NASA/TM—1998-206621/REV1

July 2010
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William O. Hughes and Anne M. McNelis

Glenn Research Center, Cleveland, Ohio

Statistical Analysis of a Large Sample Size 

Pyroshock Test Data Set Including 

Post Flight Data Assessment

NASA/TM—1998-206621/REV1

July 2010

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135

Prepared for the

80th Shock and Vibration Symposium

sponsored by the Shock and Vibration Information Analysis Center (SAVIAC)

San Diego, California, October 25–29, 2009
Acknowledgments

The authors would like to acknowledge the efforts of the following organizations and individuals that consented and cleared 

the AC-141 fl ight shock data measurements for public release: Lockheed Martin Space Systems Company/Mike Kramer, Peter 

Turchick, Brian Emmet; United Launch Alliance/Bill Anderson, Jim Oates; NASA Kennedy Space Center/Chris Gerace. 

Available from

NASA Center for Aerospace Information

7115 Standard Drive

Hanover, MD 21076–1320

National Technical Information Service

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Alexandria, VA 22312

Available electronically at http://gltrs.grc.nasa.gov

Trade names and trademarks are used in this report for identifi cation 

only. Their usage does not constitute an offi cial endorsement, 

either expressed or implied, by the National Aeronautics and 

Space Administration.

Level of Review: This material has been technically reviewed by technical management. 
NASA/TM—1998-206621/REV1 1 

Statistical Analysis of a Large Sample Size Pyroshock Test 

Data Set Including Post Flight Data Assessment 

William O. Hughes and Anne M. McNelis 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Abstract 

The EOS Terra spacecraft launched on an Atlas IIAS launch vehicle on its mission to observe planet 

Earth in late 1999. Prior to launch, the new design of the spacecraft’s pyroshock separation system was 

characterized by a series of thirteen separation ground tests. The analysis methods used to evaluate this 

unusually large amount of shock data will be discussed in this paper, with particular emphasis on 

population distributions and finding statistically significant families of data, leading to an overall shock 

separation interface level. The wealth of ground test data also allowed a derivation of a Mission 

Assurance level for the flight. All of the flight shock measurements were below the EOS Terra Mission 

Assurance level thus contributing to the overall success of the EOS Terra mission. The effectiveness of 

the statistical methodology for characterizing the shock interface level and for developing a flight Mission 

Assurance level from a large sample size of shock data is demonstrated in this paper. 

Introduction 

In the aerospace industry, the availability of a meaningful valid set of pyroshock test data is often 

difficult to obtain. Obtaining a large sample size of such data is very rare. However, a large sample size 

pyroshock test data set was obtained for a newly designed spacecraft separation system which was 

employed for the EOS (Earth Observing System) Terra NASA mission. On December 18, 1999, NASA 

launched the EOS Terra spacecraft to low Earth orbit, on a Lockheed-Martin Atlas IIAS (Atlas-Centaur141) launch vehicle. Due to EOS’s truss structure and hard-point spacecraft interface, the pyroshock 

spacecraft separation system utilized for this mission was a new design. This separation system was test 

verified through numerous ground test firings, by both the launch vehicle contractor and the spacecraft 

contractor. This resulted in an unusually large amount of shock test data. The availability of such a test 

data set allows a statistical evaluation of shock data which is seldom employed. Emphasis will be given to 

the population distribution of each data set and the proper combination of different data sets. Additionally 

the binomial distribution will be used to better characterize the separation shock interface level for this 

particular separation system. In this paper, a comparison is also provided of the actual AC–141 flight 

shock levels from the spacecraft separation event with the expected shock level that was derived from the 

assessment of the ground test data. 

Spacecraft Separation System 

As part of the Lockheed-Martin Astronautics (LMA) IELV (Intermediate Expendable Launch 

Vehicle) Program, a 77 in., six point hard-point payload separation system (PSS77) was developed to 

provide structural attachment of the EOS spacecraft to the launch vehicle’s payload adapter (PLA) during 

launch and ascent, until the operation of the system releases the spacecraft. Since EOS was the first 

mission using the PSS77, extensive testing of the system was performed by both the launch vehicle 

contractor (LMA, at Denver) and the spacecraft contractor (LMMS, Lockheed-Martin Missiles & Space, 

at Valley Forge). 

The PLA is an inverted conical skin-stringer-ring structure. The six shear plates which mount on the 

forward ring of the PLA (as seen in Fig. 1(a)) correspond to the six nodes or hard-points of the spacecraft. 

As shown in Figure 1(b), each shear plate is attached to the PLA by a separation stud and nut. The 
NASA/TM—1998-206621/REV1 2 

spacecraft hard-points are connected to the shear plates by a number of tension bolts. When the separation 

nut pressure cartridge fires, the separation stud is released and is caught by the stud catcher assembly. 

Separation occurs between the PLA and the separation plate (which is now attached to the spacecraft). 

The separation impulse is provided by springs at each of the six nodes. 

(Ref. 1) 

(Ref. 1) 
NASA/TM—1998-206621/REV1 3 

Test Configurations 

The test firing of the PSS77 was tested in different hardware configurations at LMA and at LMMS 

due to different organizational purposes. 

The testing at LMA was done to verify the mechanical operation of the PSS77, especially the stud 

catcher design and to acquire and characterize the pyroshock levels produced by the separation system at 

various separation stud preload values. A total of twelve test firings were performed over three different 

test series at LMA (Ref. 1), which occurred from January 1996 through February 1997. Two test firings 

were performed at LMMS (Ref. 2) in June and July 1996. Since LMMS is the EOS spacecraft contractor, 

the primary purpose of their testing was to acquire and characterize the pyroshock levels propagating 

from the spacecraft interface up the spacecraft. Hence two different test configurations were tested. 

The LMA test configuration is shown in Figure 2. Approximately one-third of the full spacecraft 

mass of 11,000 pounds was simulated using the spacecraft stiffness simulator (SCSS). A flight-like PLA, 

a Centaur Equipment Module (CEM) with avionics components and a stub adapter were utilized. At 

separation, a mass counterweight was used to achieve the correct flight separation velocity for the SCSS. 

The PLA, CEM and stub adapter remained attached to the base fixture. Data was obtained at the six shear 

plate locations, at three PLA locations and at various components of the CEM. LMA acquired their test 

data on analog tape recorders (Honeywell). 

The LMMS test configuration is shown in Figure 3. A full scale spacecraft simulator (11,000 pounds) 

with mass models for spacecraft instruments was utilized. A short CEM simulator without avionics 

hardware was used. No stub adapter was present in this testing. An overhead crane suspended the EOS 

spacecraft and PLA/CEM simulator assembly. At separation, the PLA/CEM simulator dropped 

approximately 3 in. onto a foam shock absorber pad. Shock data was obtained at the identical six shear 

plate and three PLA locations (as the LMA testing) and at numerous spacecraft instruments locations. 

LMMS acquired their test data digitally (Zonic). 

Description of Test Series 

The first series of testing, denoted as LMA 1-5, consisted of five separation firings. This testing was 

performed at LMA’s Denver (Waterton) test facility, as were all the other LMA test series. Testing 

occurred from January 1996 through April 1996. Various stud preloads were tested (ranging from a very 

low value of 10,900 pounds to a high value of 24,000 pounds). Both developmental and qualified stud 

catchers were employed in this series as the stud catcher performance was being evaluated. (A sixth test, 

LMA 6, was also performed in this series. The purpose of LMA 6 was to measure the effect of ordnance 

sequencing on the shock levels. Although firing the separation nuts at different times did not significantly 

affect the shock levels, the data from this test was not utilized in the statistical study of this work. ) 

The second series of testing is denoted as LMMS 1-2 and occurred at Valley Forge. Testing was 

performed in June-July 1996. The nominal stud preload of 20,700 pounds were utilized in both of the two 

test firings. 

The third series of testing was denoted as LMA 7-9. These three test firings occurred in SeptemberOctober 1996. For the CEM avionics boxes, higher fidelity avionics simulators were employed and some 

new lower fidelity mass simulators were utilized starting with LMA test 7. A low, nominal and high stud 

preload were tested. Additionally, a positive stud retraction method was added to the stud catcher design 

starting with LMA test 7. 
NASA/TM—1998-206621/REV1 4 

(Ref. 1) 

(Ref. 2) 
NASA/TM—1998-206621/REV1 5 

The fourth and last series of testing was LMA 10-12. These three test firings occurred in February 

1997. Again a low, nominal and high stud preload were tested. The separation nuts for LMA 10-12 were 

taken from a different production lot than all the rest of the EOS test firings. Also, a different CEM was 

utilized for this testing, along with two more additional CEM simulators. 

A summary of the four test series is provided in Table 1. Endevco’s 7255A accelerometers were used 

to measure the shock at the shear plate locations (see Fig. 1(b)) and at the payload adapter (PLA) 

locations for all four test series. All the shear plate data discussed in this paper is from the axial 

measurements, which was generally five to ten times larger in magnitude than the radial or tangential 

measurements at the shear plate locations. Note that unless otherwise stated, the statistical analysis 

discussed in the next four sections of this paper utilizes the ground test measurements at the shear plate 

locations to determine the separation interface shock level. 

TABLE 1.—SUMMARY OF TEST SERIES 

TEST 

SERIES 

CONFIGURATION 

& TEST SITE 

TEST 

DATES 

NUT 

PRELOAD 

VALUES 

NUT 

PRODUCTION LOT 

LMA 1-5 #1 Denver Jan. 96 - 

April 96 

very low to high # 1 

LMMS 1-2 #2 Valley Forge June 96 - 

July 96 

nominal # 1 

LMA 7-9 #1 Denver Sept. 96 - 

Oct. 96 

low, nominal, 

high 

# 1 

LMA 10-12 #1 Denver Feb. 97 low, nominal, 

high 

# 2 

Statistical Analysis of Each Test Series 

Each of the four test series was first analyzed to determine its probability distribution. A large data 

population is generated for each test series by combining all one-sixth octave bands into a single data base 

by using the method described by Manning (Ref. 3). Each shock response level (at each frequency) was 

normalized to have zero mean and unit variance. For example, for the LMA 1-5 test series, a normalized 

database of size 780 was generated (5 tests x 6 measurements per test x 26 one-sixth octave bands (560 to 

10,000 Hz) per shock response measurement). 

The normalized database is analyzed to determine its probability distribution. The data from each test 

series was analyzed looking at both the measured data (normal distribution) and the log of the measured 

data (lognormal distribution). The analysis consisted of plotting probability distributions and histograms 

and calculating the median (first moment), skew (third moment) and kurtosis (fourth moment) of each 

normalized database. Duncan (Ref. 4) is a useful resource in determining significantly appropriate skew 

and kurtosis values as a function of database size. 

The conclusion was that the shock test data obtained in each of the four test series was lognormally 

distributed. This finding is consistent with past practices and with the guidelines of the NASA pyroshock 

standard (Ref. 5). The large amount of test data available in this testing enabled a statistical basis for the 

lognormal distribution instead of just assuming it to be true, as is often the case. 

Figures 4 to 7 show the shock response measurements for each of the four test series. In all cases, the 

measured data is fairly repeatable and shows a smaller test to test variability than is often seen for 

separation shock test data. 
NASA/TM—1998-206621/REV1 6 

100

1000

10000

100000

100 1000 10000

G's

Natural Frequency, Hz

Figure 4. LMA 1-5

Shear Plate Data (30 Measurements)

100

1000

10000

100000

100 1000 10000

G's

Natural Frequency, Hz

Figure 5. LMMS 1-2

Shear Plate Data (12 Measurements)
NASA/TM—1998-206621/REV1 7 

100

1000

10000

100000

100 1000 10000

G's

Natural Frequency, Hz

Figure 6. LMA 7-9

Shear Plate Data (18 Measurements)

100

1000

10000

100000

100 1000 10000

G's

Natural Frequency, Hz

Figure 7. LMA 10-12

Shear Plate Data (18 Measurements)

MAX LMA 1-9

MIN LMA 1-9 
NASA/TM—1998-206621/REV1 8 

Statistical Combination of Test Series 

At this point there are four lognormal series of data. The next question to answer is “Can we 

statistically combine any or all of these data sets?” before calculating statistical levels. The criterion used 

for a successful combination was twofold. First, the combined data set must be in itself a lognormal 

distribution. Secondly, the combination was allowed only if the individual data series has means and 

standard deviations which were not statistically significantly different with a 95% confidence level. This 

last criterion was analyzed based on F-testing of the standard deviations and t-testing of the means. 

Using these criteria, it was found that it was proper to combine LMA 1-5 and LMA 7-9. The means 

and standard deviations of these two test series were not statistically significantly different and their 

combined normalized database was lognormally distributed. Figure 8 shows this combined data set, now 

denoted as LMA 1-9. The combined data set graphically appears to be one family. 

Next, the combination of the new data set LMA 1-9 with LMMS 1-2 was analyzed. It was found to be 

an invalid combination for two reasons. First, the combined distribution was not lognormal. Secondly, the 

individual means were found to be significantly different as defined by the t-testing. Looking at Figures 5 

and 8, it appears that there are differences in the shock response between these two data sets (i.e., two 

high frequency peaks for LMA 1-9 and one high frequency peak for LMMS 1-2) to agree with the 

statistically conclusion to keep these two sets separate. It is thought that the differences in the two basic 

test configurations cause this result. 

Finally, the combination of data sets LMA 1-9 and LMA 10-12 was analyzed. In this case the 

combined distribution was lognormal and the F-test of the standard deviations passed. However, the ttesting of the means were found to be significantly statistically different and thus this combination was 

not allowed. Looking at Figure 7, one can see that the general spectral trend of LMA 10-12 is consistent 

with (the minimum and maximum of) LMA 1-9. However, the LMA 10-12 data is generally between the 

minimum and the mean of the LMA 1-9 data sets. Thus the statistical conclusions of different means are 

visualized. It is theorized that the lot to lot variation in the separation nut production lots contributed to 

this difference. (Note: the separation nuts that were used for the EOS flight is from production lot # 2, 

which appears to give lower shock levels based on the LMA 10-12 test data.) 

100

1000

10000

100000

100 1000 10000

G's

Natural Frequency, Hz

Figure 8. LMA 1-9

Shear Plate Data (48 Measurements)
NASA/TM—1998-206621/REV1 9 

Analysis of Per Nut Firing Level 

At this point, three families of shock test data exists, LMA 1-9, LMMS 1-2 and LMA 10-12 (Figs. 8, 

5 and 7). Both the LMA and the LMMS test configurations must be considered equally valid with regards 

to determining a shock interface level. Also since variation in the separation nut production lot should be 

accounted for both LMA 1-9 (Lot # 1) and LMA 10-12 (Lot # 2) need to be considered. Thus, there are 

three families of equally valid data. 

It was decided to calculate a P95/50 level (using lognormal distribution) for each of the three families. 

A maximum envelope of these three P95/50 curves was then done to define the maximum expected 

environment (MEE) for a single separation nut firing. This methodology resulted in a peak shock 

response level of 13,600 Gs. 

Analysis of Per Flight Level 

Since a “successful” flight payload separation system would consists of six separation nuts all firing 

at or below the MEE level as defined above, it was determined that the per nut MEE level was not 

sufficient for establishing the spacecraft interface level. For example, if a single nut has a P95/50 

probability of success (success defined as being at or below the P95/50 level) then firing six nuts (as in a 

flight separation) would have only a 74% probability (0.95 raised to the 6th power) that none of the six 

nuts would exceed the P95/50 level. 

The binomial distribution (Ref. 6) can be utilized to find the probability of an event happening exactly 

X times in N trials given the probability that an event will happen in any single trial. Knowing that the 

desired interface flight MEE is a P95/50 level, a new calculation can be made for an individual nut level. 

This calculation would result in an individual nut level which would ensure a P95/50 per flight level 

(firing of six nuts). 

One can calculate that a P99.1/50 per nut firing is equivalent to a P95/50 flight firing of six nuts. That 

is 0.991 raised to the 6th power is 0.95. 

Therefore a P99.1/50 level was calculated for each of the three valid families of test data. Again the 

maximum envelope of these three curves was made to calculate the new flight MEE level. Due to the fact 

that the shock test data within a family was so repeatable, the impact of allowing for the successful firing 

of all six nuts was only approximately 1 dB. The MEE level was raised from 13,600 Gs (per nut firing) to 

15,200 Gs (per flight), as a result. 

After allowing for a one-third octave shift in frequency to account for possible hardware stack up 

variation, the flight MEE level was closely enveloped to define the final Interface Control Document 

(ICD) level. This ICD level peaks at 16,100 Gs. The ICD specification is shown along with the flight 

MEE for the three families in Figure 9. 

The final ICD level was a significant reduction over the contractor’s proposed final level, and its 

implementation for the EOS Terra program resulted in saving NASA several million dollars in potential 

requalification costs of the spacecraft components. 

As a check of reasonableness, the maximum envelope of all 78 shock test measurements was 

determined and plotted against the maximum envelope of the three flight MEE curves of Figure 9. Figure 

10 shows that very similar levels are derived by the maximum enveloping technique and the statistical 

techniques for this EOS shock test data base. This similarity is due to: (1) the unusually large sample size 

(78 measurements) of test data, and (2) the relatively small test to test variability (within each test family) 

of the shock data (as compared to typical shock test data variability). Other shock test databases could 

yield different results depending on its test to test variability and the number of test measurements. 
NASA/TM—1998-206621/REV1 10 

100

1000

10000

100000

100 1000 10000

Gs

Natural Frequency, Hz

Figure 9. Comparison of 3 Flight Maximum Expected

Environments (MEE) versus Interface Specification

LMA 1-9 Flight MEE LMMS 1-2 Flight MEE

LMA 10-12 Flight MEE ICD Specification

100

1000

10000

100000

100 1000 10000

G's

Natural Frequency, Hz

Figure 10. Comparison of Maximum Enveloping Levels 

with Statistical Levels

Maximum of 78 Test Measurements

Statistical Based Level
NASA/TM—1998-206621/REV1 11 

Atlas-Centaur-141 Flight Data Analysis 

In order to verify the flight shock levels, five AC–141 flight shock measurements were obtained on 

the payload adapter (PLA) for the spacecraft separation event (Ref. 7). The five measurements consisted 

of three in the axial direction, and one each in the tangential and radial directions. These flight 

measurements were utilized as a means to determine whether the amplitude of the shock separation event 

was within expected limits. 

Prior to launch a Mission Assurance shock level was developed from the ground test data in order to 

establish an extreme expected flight shock level to which the actual flight shock levels from the spacecraft 

separation event could be compared. Since the flight data was measured on the PLA structure, the 

Mission Assurance level also needed to be based on this location. From the extensive ground test 

database, there were a total of 38 PLA axial direction ground test data measurements available (these 

measurements were in addition to the shear plate measurements described previously). 

The PLA ground test data utilized the same statistically based approach as previously described for 

the ICD level. That is: (1) three valid statistical populations (above 500 Hz due to background noise 

levels) were established, (2) an extreme expected environment (EEE) for an individual measurement was 

determined, (3) the binomial distribution was used to calculate a P99/90 per flight level; this is equivalent 

to a P99.7/90 per individual measurement level, and (4) the EEE per flight levels for the three populations 

were enveloped to arrive at the statistical based flight level. Per MIL–STD–1540C, the level of the 

extreme expected environment (EEE), used for qualification testing, is that not exceeded on at least 99% 

of flights estimated with 90-percent confidence, the P99/90 level. 

This EEE level was intended to be the Mission Assurance level, which is the level that an “acceptable 

flight” should not exceed. The Mission Assurance level would thus be the contractual “not to exceed” 

level guaranteed by LMA. When the statistical based EEE level was compared to the PLA ground “test 

data max + 3 dB” it was found that they compared very well, except in the two frequency ranges where 

the EEE levels were unnecessarily high (+6.6 dB and + 8.5 dB higher than the “maximum of all the PLA 

ground test data + 3 dB”). Thus the NASA Mission Assurance level was therefore redefined to be the 

“test data maximum + 3 dB” at all frequencies (instead of the more elaborate statistical based level). 

(Note: the differences at the two frequencies are due to relatively large standard deviations of the ground 

test data which increased the statistical level unrealistically far beyond all the measured ground test data. 

This affect was magnified due to the lognormal transformation process.) Figure 11 illustrates the 

comparison of the statistically based P99/90 and the test data “maximum + 3 dB” levels. From this figure 

it is obvious that the statistical based level is not realistic in the two frequency ranges indicated. Thus, a 

lesson learned is that it is always important to look at the range of actual data for check of reasonableness, 

especially when dealing with lognormal transformations. 

This new level was then frequency shifted by a one-third octave band and tightly enveloped to derive 

the NASA Mission Assurance level. This NASA level compared well with the LMA-derived mission 

assurance level that was eventually implemented into the official vehicle contract agreement for the EOS 

Terra mission. The NASA and LMA (labeled as “EOS Terra”) Mission Assurance levels are shown in 

Figure 12. 

EOS Terra flight measurements were made at the payload adapter region and are compared in 

Figure 12 to both the EOS Terra (LMA) Mission Assurance and the NASA recommended Mission 

Assurance levels. All flight data were below the Mission Assurance levels signifying that the AC-141 

spacecraft separation event was an acceptable event and resulted in shock levels within allowable limits 

relative to excessive shock levels which could damage the spacecraft. The flight axial direction data 

measured higher than radial and tangential direction measurements. 
NASA/TM—1998-206621/REV1 12 

100

1000

10000 

100000

100 1000 10000

G's

Natural Frequency, Hz

PLA Ground Test Data Max PLA P95/50 per flight level

PLA Ground Test Data Max+3dB PLA P99/90 per flight level

Unwarranted high

statistical levels above 

test maximum

+8.5 dB

+6.6 dB SRS Q=10 

Figure 11. Comparison of EOS Terra PLA Statistical and Maximum Levels
NASA/TM—1998-206621/REV1 13 

The same payload adapter flight data compared very well with the minimum and maximum of the 

PLA ground test data as shown in Figure 13. 

Conclusions 

The sample size is typically small for aerospace shock test data. This often forces the engineer to 

make assumptions on its population distribution and utilize conservative margins or methodologies in 

determining specifications. For example, the MEE is often derived by taking the maximum envelope of a 

limited amount of shock data and adding 3 to 6 dB. For the case of the EOS payload separation shock 

event, a large amount of shock test data was available which allowed for some unique statistical analysis 

and a more accurate definition of the interface shock specification. 

A description of the methodology employed on the EOS shock test data and the rationale for using it 

is provided in this paper. The EOS test series data for the shear plate measurements was analyzed and 

shown to be lognormally distributed for all four test series. Statistical checks were employed to validate 

when it was proper to combine test series data. It was found to be valid for only one combination. Finally, 

the binomial distribution was utilized to go from a per nut MEE level to a per flight MEE level which 

determined the final interface shock specification for the EOS spacecraft. 

This methodology resulted in the flight MEE curves and the ICD specification as shown in Figure 9. 

This ICD specification represents the expected spacecraft separation interface source shock level which in 

turn is utilized to design and qualify the spacecraft’s components. 

A similar statistical methodology was employed on the PLA ground test measurements to determine 

the Mission Assurance level. This Mission Assurance level was a contractual agreement between NASA 
NASA/TM—1998-206621/REV1 14 

and LMA which served as a basis of determining whether the actual AC-141 flight spacecraft separation 

event resulted in reasonable expected flight shock levels. Ultimately it was assessed that the ground data 

“Test Max + 3 dB” level was the better level, compared to the statistical level, from which to base the 

NASA Mission Assurance level. The statistically based level had two SRS levels that were unrealistically 

high due to the large standard deviations and subsequent lognormal transformations of the data. 

Actual flight shock measurements at the PLA location were obtained during the AC-141 flight 

(Ref. 7). As shown in Figure 12, the flight shock levels were below the Mission Assurance level which 

was indicative of an acceptable spacecraft separation event for this mission, contributing to a successful 

EOS Terra mission. For this separation system event the flight shock data in the axial direction was 

higher than for the radial and tangential directions. 

Figure 13 illustrates a unique comparison of extensive ground test data sets with the flight data at the 

same PLA location. The flight shock measurements were comparable in both level and spectral shape to 

the ground test data. 

Further information on the EOS shock separation test programs may be found in the LMA (Ref. 1) 

and LMMS (Ref. 2) contractor test reports. 

References 

1. Salmon, M, Nickel, D., 1997, “Intermediate Expendable Launch Vehicle (IELV) Payload Separation 

System - 77 Inch Test Report—Volume 1,” Lockheed Martin Astronautics Space Systems Report 

IELV-96-020. 

2. Mittal, S., Staley, J., McCue, R., 1996, “EOS AM–1 Spacecraft Structure Shock Test Final Report 

(VRD–130),” Lockheed Martin Missiles & Space Valley Forge Operations Report EOS–DN–STR–

071.

3. Manning, J.E., 1991, “Space Station Freedom Work Package 4 Acoustic and Vibration 

Environment,” Cambridge Collaborative, Inc., Report 91–12–13109–1. 

4. Duncan, A.J., 1965, Quality Control and Industrial Statistics, Richard D. Irwin, Inc., Homewood, IL, 

pp. 916.

5. NASA–STD–7003, NASA Technical Standard on Pyroshock Test Criteria, May 18, 1999. 

6. Spiegel, M.R., 1961, Statistics, McGraw-Hill Book Company, pp 122. 

7. “AC-141 First Flight Items—Flight Data Review,” Lockheed Martin, February 2000. 
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Hughes, William, O.; McNelis, Anne, M. 

5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

WBS 432938.11.01.03.01.02.02 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration 

John H. Glenn Research Center at Lewis Field 

Cleveland, Ohio 44135-3191 

8. PERFORMING ORGANIZATION

 REPORT NUMBER

E-11057-1 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration 

Washington, DC 20546-0001 

10. SPONSORING/MONITOR'S

 ACRONYM(S)

NASA 

11. SPONSORING/MONITORING

 REPORT NUMBER

NASA/TM-1998-206621-REV1 

12. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified-Unlimited 

Subject Categories: 15 and 18 

Available electronically at http://gltrs.grc.nasa.gov 

This publication is available from the NASA Center for AeroSpace Information, 443-757-5802

13. SUPPLEMENTARY NOTES

14. ABSTRACT

The Earth Observing System (EOS) Terra spacecraft was launched on an Atlas IIAS launch vehicle on its mission to observe planet Earth in 

late 1999. Prior to launch, the new design of the spacecraft’s pyroshock separation system was characterized by a series of 13 separation 

ground tests. The analysis methods used to evaluate this unusually large amount of shock data will be discussed in this paper, with particular 

emphasis on population distributions and finding statistically significant families of data, leading to an overall shock separation interface 

level. The wealth of ground test data also allowed a derivation of a Mission Assurance level for the flight. All of the flight shock 

measurements were below the EOS Terra Mission Assurance level thus contributing to the overall success of the EOS Terra mission. The 

effectiveness of the statistical methodology for characterizing the shock interface level and for developing a flight Mission Assurance level 

from a large sample size of shock data is demonstrated in this paper.

15. SUBJECT TERMS

Statistical analysis; Pyroshock separation system testing; Spacecraft qualification; Dynamics 

16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

 ABSTRACT

UU 

18. NUMBER

 OF 

 PAGES

20 

19a. NAME OF RESPONSIBLE PERSON

STI Help Desk (email:help@sti.nasa.gov) 

a. REPORT

U 

b. ABSTRACT

U 

c. THIS 

PAGE

U 

19b. TELEPHONE NUMBER (include area code)

443-757-5802 

Standard Form 298 (Rev. 8-98)

Prescribed by ANSI Std. Z39-18