June 2011 

NASA/TM-2011-217151 

NESC-RP-10-00629 

 

Development and Certification of 

Ultrasonic Background Noise Test (UBNT) 

System for use on the International Space 

Station (ISS) 

William H. Prosser/NESC 

Langley Research Center, Hampton, Virginia 

Eric I. Madaras 

Langley Research Center, Hampton, Virginia 
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June 2011 

NASA/TM-2011-217151 

NESC-RP-10-00629 

 

Development and Certification of 

Ultrasonic Background Noise Test (UBNT) 

System for use on the International Space 

Station (ISS) 

William H. Prosser/NESC 

Langley Research Center, Hampton, Virginia 

Eric I. Madaras 

Langley Research Center, Hampton, Virginia 
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NASA Engineering and Safety Center 

Technical Assessment Report 

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Title: 

Development and Certification of Ultrasonic Background Noise 

Test (UBNT) System for use on the International Space Station 

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Development and Certification of Ultrasonic Background Noise Test 

(UBNT) System for use on the 

International Space Station (ISS) 

May 5, 2011 
NASA Engineering and Safety Center 

Technical Assessment Report 

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Report Approval and Revision History 

Approval and Document Revision History 

Approved 

Version 

 

1.0 NESC Director Date 

Version Description of Revision Office of Primary 

Responsibility

Effective Date 

1.0 Initial Release Dr. William Prosser, 

NASA Technical Fellow 

for Nondestructive 

Evaluation (NDE), 

LaRC 

May 5, 2011 
NASA Engineering and Safety Center 

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Table of Contents 

Volume I: Technical Assessment Report 

1.0 Notification and Authorization ............................................................................................. 5

2.0 Signature Page ........................................................................................................................ 6

3.0 Team List ................................................................................................................................ 7

4.0 Executive Summary ............................................................................................................... 8

5.0 Assessment Plan ................................................................................................................... 12

6.0 Proposed Solution ................................................................................................................ 15

6.1 Proposed Hardware Solutions ................................................................................................ 16

6.2 Proposed Software Solutions ................................................................................................. 17

6.3 Proposed Certification Solutions ........................................................................................... 18

7.0 Implementation .................................................................................................................... 19

7.1 UBNT Hardware Modification Implementation .................................................................... 19

7.1.1 RSU Transceiver Module ......................................................................................... 19

7.1.2 RSU Sensor Module ................................................................................................. 20

7.1.3 RTV142 Adhesive .................................................................................................... 24

7.2 UBNT Software Modification Implementation ..................................................................... 25

7.2.1 RSU Flight Control Software GUI ........................................................................... 25

7.2.2 Automatic Communications with the Transceiver .................................................... 27

7.2.3 Verify Operations ..................................................................................................... 27

7.2.4 Test Operations ......................................................................................................... 28

7.2.5 Data Downloading Operations .................................................................................. 29

7.2.6 Memory Management ............................................................................................... 30

7.3 UBNT Certification ............................................................................................................... 32

7.3.1 Requirements ............................................................................................................ 32

7.3.2 Certification Testing ................................................................................................. 33

7.3.3 Functional Testing .................................................................................................... 36

7.3.4 Documentation .......................................................................................................... 37

8.0 Findings, Observation, and NESC Recommendations ..................................................... 39

8.1 Findings ................................................................................................................................. 39

8.2 Observation ............................................................................................................................ 39

8.3 NESC Recommendations ....................................................................................................... 39

9.0 Alternate Viewpoints ........................................................................................................... 40

10.0 Other Deliverables ............................................................................................................... 40

11.0 Lessons Learned ................................................................................................................... 40

12.0 Definition of Terms .............................................................................................................. 40

13.0 Acronyms List ...................................................................................................................... 41

14.0 References ............................................................................................................................. 43
NASA Engineering and Safety Center 

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List of Figures 

Figure 5.0-1. Test Concept ............................................................................................................. 13 

Figure 5.0-2. Proposed Node 3 Sensor Configuration .................................................................... 14 

Figure 5.0-3. Proposed US Laboratory Sensor Configuration ........................................................ 15 

Figure 7.1-1. (a) UBNT RSU Transceiver Module, (b) UBNT USB Cable with Velcro 

Cable Wrap, and (c) UBNT USB Connectors .......................................................... 19 

Figure 7.1-2. RSU Transceiver Module Modified for an External Battery (top right) and 

External Antenna Connection (top left). ................................................................... 20 

Figure 7.1-3. SSP WLEIDS L91 Battery Pack with External Connection ..................................... 21 

Figure 7.1-4. RSU Module with the WLEIDS L91 External Battery and 2 m External 

Antenna ..................................................................................................................... 21 

Figure 7.1-5. RSU Low Frequency Response Connected to the B225.5 Sensors after 

10 milli-g Acceleration Excitation ............................................................................ 24 

Figure 7.1-6. RTV Syringe Dispenser ............................................................................................ 25 

Figure 7.1-7. RTV Loaded Syringe ................................................................................................ 25 

Figure 7.2-1. RSU Flight Control Software GUI ........................................................................... 26 

Figure 7.3-1. EMI Test Results ...................................................................................................... 35 

Figure 7.3-2. UBNT Drawing Tree ................................................................................................ 37 

List of Tables 

Table 7.1-1. Gain/Frequency Values Model for the RSU Sensor Modules. ................................. 23 

Volume II: Appendices 

Appendix A. SDTO Flight Software Manual ...................................................................... 45 
NASA Engineering and Safety Center 

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Test (UBNT) System for use on the International Space Station 

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Volume I: Technical Assessment Report

1.0 Notification and Authorization 

Dr. William Prosser, NASA Technical Fellow for Nondestructive Evaluation (NDE), requested the 

NASA Engineering and Safety Center (NESC) to participate in the development of a Station 

Development Test Objective (SDTO) to characterize the ultrasonic background noise that exists in 

the International Space Station (ISS). 

The requirement for this work was identified in the ISS Integrated Risk Management Application 

(IRMA), Watch Item #4669, which addresses the need for a leak detection/location system. The 

NESC was ideally situated to contribute to this investigation because of their history with pioneering 

the study of a compact, low power, high speed digitizing system known as the Distributed Impact 

Detection System (DIDS). These vehicle health monitoring devices were evaluated in a previous 

NESC assessment study and deemed to have significant potential for safety and space flight 

applications [ref. 1]. 

A joint NESC/ISS effort was proposed to the NESC as an out-of-board activity. Dr. Eric Madaras at 

Langley Research Center (LaRC) was selected to lead this assessment. The investigation plan was 

presented to the ISS Vehicle Control Board (VCB) and the NESC Review Board (NRB) and 

approved by the respective boards on March 31, 2010, and April 10, 2010. This report was presented 

to the NRB on May 5, 2011. 

The key stakeholders for this assessment include the ISS Program (ISSP) and Exploration Systems 

Mission Directorate.
NASA Engineering and Safety Center 

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2.0 Signature Page 

Submitted by: 

___________________________________ __________________________________ 

Dr. William H. Prosser Date Dr. Eric I. Madaras Date 

___________________________________ 

Mr. Todd C. Hong Date 

Signatories declare the findings and observations compiled in the report are factually based from 

data extracted from Program/Project documents, contractor reports, and open literature, and/or 

generated from independently conducted tests, analysis, and inspections. 
NASA Engineering and Safety Center 

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3.0 Team List 

Name Discipline Organization 

Core Team 

William Prosser NESC Lead LaRC/NESC 

Eric Madaras Principle Investigator LaRC/NESB 

Todd Hong Investigation Engineering Lead JSC/EV17 

John P. Dempsey UBNT Investigation Manager JSC/OB 

Ladessa Hicks-Jones UBNT Investigation Lead JSC/OB 

David S. Havermalz Investigation Engineer JSC/EV4 

Kornel Nagy Structures and Mechanics Lead JSC/ES 

Jailin Tian Analysis Lead LaRC/FSSB 

Aaron Trott DIDS Lead Engineer Invocon, Inc. 

Roy Savage MTSO Program Analyst LaRC 

Administrative Support 

Erin Moran Technical Writer LaRC/ATK
NASA Engineering and Safety Center 

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4.0 Executive Summary 

As a next step in the development and implementation of an on-board leak detection and 

localization system on the International Space Station (ISS), there is a documented need to 

obtain measurements of the ultrasonic background noise levels that exist within the ISS. This 

need is documented in the ISS IRMA, Watch Item #4669. To address this, scientists and 

engineers from the Langley Research Center (LaRC) and the Johnson Space Center (JSC), 

proposed to the NASA Engineering and Safety Center (NESC) and the ISS Vehicle Office a joint 

assessment to develop a flight package as a Station Development Test Objective (SDTO) that 

would perform ultrasonic background noise measurements within the United States (US)-

controlled ISS structure. 

Formal investigation approval was received from the ISS Vehicle Control Board (VCB) and the 

NESC on March 31, 2010, and April 10, 2010, respectively. This investigation required the 

modification of existing Distributed Impact Detection System (DIDS) units (or Remote Sensor 

Units (RSUs)) and the acquisition of additional hardware, software modifications, and the 

hardware certification as a SDTO. The certification included meeting the Space Shuttle Program 

(SSP) 50835, ISS Pressurized Volume Hardware Common Interface Requirements Document 

(CIRD) certification, which allowed the SDTO package to be launched on any ISS-approved 

vehicle. A Change Request (CR) 012334 was submitted to the Space Station Program Control 

Board and approved on July 13, 2010, to support launching the SDTO and the operational 

support on the ISS once the SDTO was on orbit. 

At the start of this investigation, the NESC team had six RSUs, two transceiver units, and 

40 transducers that could be applied to the SDTO. The first phase involved purchasing 

additional hardware to satisfy the SDTO requirements. Three additional RSUs, two transceivers, 

and 38 flight sensor cables were procured. All of the RSU hardware and software were modified 

to improve their capabilities for the ISS application. The system hardware modifications made 

included: changing the RSU power source to allow operation on the L91 battery system that is 

currently in use on the SSP’s Orbiter Wing Leading Edge Impact Detection System (WLEIDS) 

and employing an external antenna for more reliable communications. System software changes 

implemented included the ability to trigger the RSUs on a programmable time schedule along 

with a method to monitor the system’s progress during the programmed triggering schedules. 

Other software changes involved: adding the capability to automatically open the universal serial 

bus (USB) port when the software’s graphical user interface (GUI) was activated; increasing the 

number of files that could be saved in the memory by tenfold; adding a summary file handling 

capability to the sensor units; adding a software configuration file capability so ground-based 

developed files could be uploaded and executed; and developing a software application to 

streamline on-orbit operations. 
NASA Engineering and Safety Center 

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Test (UBNT) System for use on the International Space Station 

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In parallel with the hardware developments, flight unit certification was initiated to SSP 50835. 

Meeting SSP 50835 requirements implies by internal references meeting all the other necessary 

ISS certification documents. Initial tests included Offgas Testing for the hardware and adhesive 

materials, electromagnetic interference (EMI) emission, EMI susceptibility for the full system, 

and radiation susceptibility testing. Once all of the hardware was received, certification 

continued with Materials Certification; Thermal Analysis; Strength, Fracture, and Venting 

Assessment; Radio Frequency Authorization; Toxicology Assessment; Software and Hardware 

Support Station Computers (SSC) Integration Test; Wiring Continuity; Dielectric Withstanding 

Voltage and Insulation Resistance Testing; Circuit Derating Analysis; and Safety Certification. 

The initial investigation plan targeted flight on SSP flight Space Transportation System 

(STS)-134. This required the SDTO be completed with all required certifications signed and 

shipped to the Kennedy Space Center (KSC) by December 19, 2010. This SDTO was ranked as 

a low priority, thus there was a possibility that another package with a higher priority could 

displace this SDTO from the flight. An opportunity was identified to make a late load on the 

European Space Agency’s (ESA) Autonomous Transfer Vehicle (ATV)-2, scheduled to launch 

prior to STS-134. The remaining certification work was rescheduled, successfully accomplished, 

and the SDTO package was shipped to KSC on November 29, 2010, for Preship Review. The 

final certification documentation was signed on December 6, 2010, one week ahead of the 

ATV-2 late load deadline. The SDTO was shipped to Kourou, French Guiana on January 6, 

2011, and was launched aboard ATV-2 on February 16, 2011. The SDTO is scheduled to start 

operations in the May 2011 time frame. 

The initial SDTO testing will measure the noise levels in the Node 3 and the US Laboratory. 

Both ISS modules provide unique opportunities to characterize potential noise sources. The 

Node 3 module houses several life support functions: water purification system, oxygen 

regeneration system, air revitalization system, lavatory system, treadmill, and the standard 

airflow and thermal control systems. The US Laboratory has 23 rack bays that can house 

numerous ISS experiments including several zero gravity experiments and the standard life 

support systems. The systems housed within these two modules have the potential to generate 

ultrasonic noises into the structure. Measurements in these two modules should give a broad 

representation of many of the sources that might exist on other similarly manufactured US 

modules and future spacecraft. Subsequent to these measurements, plans are being developed to 

extend this SDTO (i.e., Phase II) to make similar measurements in the international partner 

modules. 

The following NESC team findings were identified during this assessment development: 

(1) The RSU hardware and software necessary to perform an SDTO to characterize the 

ultrasonic background noise on the ISS was successfully acquired, modified, tested, and 

certified. It was installed onto ESA’s ATV-2 and successfully launched on 

February 16, 2011. It is tentatively expected that the operational phase for the SDTO will 
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Test (UBNT) System for use on the International Space Station 

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begin in May 2011. Pending successful completion of this SDTO, this equipment can be 

re-utilized for Phase II measurements of the ultrasonic background noise in the modules 

of the international partners. 

(2) It was noted that there is a lack of instrumentation that can provide a controlled input 

signal, which can perform a simple quantitative assessment of the transducer and 

system’s response on-orbit. 

(3) During certification testing, the RSU did not fully pass the EMI emissions and 

susceptibility testing. 

(4) The 2 GB Micro-Secure Data (SD) cards demonstrated radiation susceptibility during 

dynamic testing that translated into a mean time between failures (MTBF) of 

54.6 to 473 days. 

(5) The Micro-SD cards are a pending RSU weak link as the 2 GB storage size will soon be 

obsolete. Obsolescence could happen within 2 years. In addition, it is noted that the 

RSU in its current configuration has reached numerous software, firmware, hardware. 

and operational limitations. 

The following NESC team observations were identified in the investigation execution: 

(1) The RSUs originally procured in a previous NESC assessment [ref. 1] (two units) and the 

DIDS delivered under the original Small Business Innovation Research (SBIR) contract [ref. 2] 

(four units) were utilized for this SDTO to minimize fiscal year 2010 costs; and (2) There were 

requests to utilize the RSUs to support other NASA needs for Integrated Vehicle Health 

Monitoring (IVHM) efforts but which could not be supported because the hardware was 

dedicated for the flight SDTO.

The NESC recommendations identified are: (1) The ISSP should complete the SDTO Phase I 

data acquisition and analysis, and plan for a Phase II effort to extend the SDTO for the 

Ultrasonic Background Noise Tests (UBNT) to international partner modules; (2) The ISSP 

should assess the results of this SDTO to determine the ability to detect and locate leaks and 

predict damage locations; (3) The ISSP, in preparation for leak location or impact detection 

operations, should plan to develop a quantitative method and instrumentation to verify system 

operation while on orbit; (4) Future NASA RSU acquisitions that utilize the external antenna 

should be made with a metal enclosure to provide EMI and radiation shielding; and (5) The 

NASA Program offices should continue RSU improvements to address the Micro-SD card 

obsolescence and operational/functional flexibility to support their program needs. These 

include: 

1. Improve the RSU data storage system by either modifying the system to read larger 

capacity Micro-SD cards or by installing permanent memory that would replace the 

Micro-SD card. 

2. Improve the system’s wake-up time to be less than 10 μsec to allow the system to capture 

faster events and help reduce power consumption. 

3. Improve the analog front-end to increase RSU flexibility for other applications and avoid 
NASA Engineering and Safety Center 

Technical Assessment Report 

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Title: 

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Test (UBNT) System for use on the International Space Station 

(ISS)

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the use of “haywires” (i.e., miniature add-on circuit boards), and provide for better 

filtering and clamping when using other transducer types. 

4. Increase RSU program memory to allow the addition of new features involved with 

advanced IVHM applications. 

5. Implement the automatic triggered channel identification. 

6. Refine the internode synchronization to enable multiple sensor units to be synchronized, 

which is useful for analyzing signals covered by multiple, independent sensor units. 

7. Implement fully automated command file processing to minimize/eliminate on-orbit crew 

interaction and to enable ground support crew to perform all system operations remotely. 

8. Increase the data file acquisition length to allow the ability to continuously write data to 

non-volatile memory. 

Overall, these improvements would greatly extend the RSU IVHM capabilities, increasing the 

RSU flexibility and value for future space and aeronautic applications. 
NASA Engineering and Safety Center 

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5.0 Assessment Plan 

Ultrasonic methods have been used to help detect and locate leaks and predict damage locations 

within geometrically simple ground-based structures [ref. 3]. To extend these methods to 

applications on more geometrically complex structures that support operational functions 

(e.g., space flight structures), several key, fundamental elements must be addressed. One 

primary element is an understanding of the signal-to-noise levels that exist within an operating 

structure. Active (i.e., noisy) structures (pumps, turbines, high speed flowing liquids) will 

saturate (i.e., blind) measurement systems to the critical ultrasonic signals that arise from damage 

or leak generated signals. Although there are low frequency accelerometer data from spacecraft 

structures and audible airborne noise data, to date, there are no known measurements of the 

ultrasonic structural borne background noise levels that have been made on orbit due to the lack 

of operational instrumentation or systems. This lack of operational instrumentation and 

equipment is the second missing element that is required [ref. 3]. This involves the need for 

compact, ultra low power hardware that is able to function in a space environment. Most 

existing instrumentation is unsatisfactory for this need. Over the past few years, a compact 

DIDS data acquisition system was developed under an SBIR effort, which appears to meet most 

of the requirements for on-orbit use. The DIDS was studied in an earlier NESC assessment 

[ref. 1]. 

The ISS maintains an integrated risk management database, the IRMA, which documents the 

need for having a leak location method. It is understood that the measurement system designed 

for the purpose of locating atmospheric leaks must have an adequate signal-to-noise level to 

work satisfactorily. IRMA Risk 4669 specifies the requirement to make background ultrasonic 

noise measurements within the ISS to characterize the necessary signal-to-noise levels that might 

exist within the ISS. To address this need, scientists and engineers from LaRC and JSC 

developed a plan to fly a set of hardware capable of making the needed ultrasonic measurements 

within the ISS structural wall. The system would incorporate modified RSUs that would be 

appropriate for such a flight investigation. This report describes the efforts to prepare the flight 

package to address this need. Certification and functional testing of the hardware and software 

for flight would represent the necessary assessment plan. Data acquired by the on-orbit UBNT 

will aid in the development of future leak location systems. 

The initial testing with this hardware will measure the noise levels present in the Node 3 and the 

US Laboratory. Figure 5.0-1 shows the concept of the UBNT SDTO in operation. Both ISS 

modules provide unique opportunities to characterize potential noise sources. The Node 3 

currently houses several life support functions and standard airflow and thermal control systems. 

Figure 5.0-2 shows the present planned configuration for testing in the Node 3. The US 

Laboratory has 23 rack bays that can house numerous ISS experiments and standard life support 

systems. Figure 5.0-3 shows the present planned configuration for testing in the US Laboratory. 

The systems housed within these two modules have the potential to generate ultrasonic noises 
NASA Engineering and Safety Center 

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Test (UBNT) System for use on the International Space Station 

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into the structure. Measurements in these two modules should provide a broad representation of 

many of the sources that might exist on other similarly manufactured modules and future 

spacecraft. Subsequent to these measurements, plans are being made to extend this SDTO 

(Phase II) to make similar measurements in the ISS international partner modules. 

Figure 5.0-1. Test Concept 
NASA Engineering and Safety Center 

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Figure 5.0-2. Proposed Node 3 Sensor Configuration 
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Figure 5.0-3. Proposed US Laboratory Sensor Configuration 

6.0 Proposed Solution 

The initial test plans for this SDTO called for nine RSUs, four transceiver units, and 

38 transducers with the associated cabling. At the onset, the NESC team possessed six RSUs, 

two transceiver units, and 40 transducers, thus necessitating the procurement of additional 

hardware. In addition, modifications to the existing and new hardware were required to address 

several concerns. These concerns included: the safety of the internal battery (i.e., lithium (Li) 

thionyl chloride chemistry) used within the RSU; the internal antenna’s ability to successfully 

transmit and receive signals from behind racks and panels; and a desire for larger memory 

storage capabilities and higher signal gains. There were software modifications required 

including more flexible triggering capability, automatic selection of the USB port on startup, and 

a simpler GUI. Other software modifications included the implementation of a summary data 

file that could be downloaded for a rapid initial evaluation, the ability to upload a configuration 
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file that would automatically set test and download parameters, and increasing the number of 

files that could be addressed to more than 999. The configuration file was necessary to allow 

ground support personnel to set up tests and download data, thus reducing on-orbit crew time 

requirements. 

Once these issues were addressed, the hardware had to undergo required flight certifications 

steps, which are identified in ISSP SSP 50835. Meeting these requirements would give NASA 

the most flexibility for launching the SDTO and simplifying the future development and 

certification of a leak location system based on this type of hardware. 

6.1 Proposed Hardware Solutions 

To satisfy hardware needs, three RSUs, two transceivers, and 38 flight sensor cables 

(2-meter nominal length) were purchased. In parallel with the acquisition of additional 

hardware, modifications to address battery, radio frequency (RF) communications, higher gain 

levels, and memory concerns were pursued. 

The original RSUs utilized a Li thionyl chloride battery, which is prohibited from use on the ISS. 

To satisfy the concerns about the battery chemistry, it was decided that the RSUs would be 

converted to use the battery type used in SSP Orbiter WLEIDS, which are model L91 Li iron 

disulfide chemistry AA batteries. This battery change had several advantages. Most important, 

the L91 batteries meet SSP flight certification and safety requirements, making certification for 

the ISS easier. Secondly, the L91 batteries offer twice the battery power over the Li thionyl 

chloride battery. The only disadvantage to the L91 batteries was their size being too large to fit 

inside the RSU case. This required a modification to bring the power connector outside the case. 

To improve RF communications within the ISS, it was decided to replace the internal antenna 

with a connector that passed through the RSU case allowing the use of a small, unobtrusive 

external antenna. A 2-meter long cable was specified to make the antenna connection between 

the RSU mounted behind a rack and the antenna mounted within the ISS corridors. This allowed 

near line of sight to the transceiver in the ISS module. An antenna mount was developed that 

would orient the antenna perpendicular to the mounting surface. Testing conducted in ISS 

mockups demonstrated that this orientation provided the optimum signal within ISS mockups. 

The RSUs utilize Micro-SD cards for memory storage. Increasing the memory capacity 

consisted of replacing the existing Micro-SD cards (250 MB capacity) with a card with a larger 

capacity. The RSU software had, in principle, the capability to address a Micro-SD card with a 

2 GB capacity, although the software had not been certified to that level. 

The final hardware modification was the need for higher signal amplification (gain). The 

existing RSUs had a maximum low frequency gain of 15, which is sufficient for impact 

detection. Field tests with laboratory equipment showed that gains of 200 were a more optimal 

gain level for leak signals. In addition, those field tests indicated that the frequency of the leaks 
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ranged from below 40 kHz to above 500 kHz, with the greatest signal levels at the lower 

frequency range. The gain-bandwidth product (i.e., functional constant for a given amplifier 

related to the power of that amplifier) occurred near 1 MHz for the gain setting of 15. The gainbandwidth product dropped to about 700 kHz for a gain of about 25. Since the sensors being 

used had a bandwidth limit of about 330 kHz, the required Nyquist sampling frequency would 

have to be above 660 kHz. The RSU sampling rate is typically near 800 kHz, so the 700-kHz 

range for the gain-bandwidth product should produce an undistorted signal. Since the RSUs are 

based on a 16-bit digitizer (with about 14 bits of true dynamic range), their dynamic range made 

a gain of 25 adequate for the ISS application. This level of signal resolution along with the gain 

level should allow adequate detection of small and large noise levels ranging between the noise 

floor of the RSUs and the RSU’s saturation level. 

In addition to the instrumentation and software, the materials, mechanisms, and processes to 

install the sensors, hardware, and cabling were developed and evaluated. Materials and 

Processing personnel at JSC suggested that room temperature vulcanizing (RTV142) be 

investigated, which exhibited a low volatile organic compound (VOC) character. 

6.2 Proposed Software Solutions 

The DIDS was originally designed with the purpose of triggering unscheduled impact sounds. 

For the purposes of this SDTO, it was required that the units be configured to allow time 

scheduled measurements during various on-orbit activities. Hence, it was requested that 

Invocon, Inc. modify the software to allow the system to execute a series of triggers during 

specific time windows. It was decided to allow up to 16 windows of data acquisition time. In 

addition, the windows could be of variable time length to allow either short or long data 

acquisition windows, with variable times between windows. During a data acquisition window, 

the time between the individual triggers could be adjusted. Measurements within the Node 3 

during ground certification testing indicated that a 15-second spacing minimum would be 

adequate for detecting mechanical noise sources. It was considered a possibility that the ISS 

crew might not be able to start the software in a timely manner (i.e., a scheduled test might be 

targeted for a specific time, but due to higher priority activities the crew might not activate the 

software when planned). To deal with this contingency, a software filter was added to allow a 

test to proceed at the next appropriate time for acquiring data. 

Another issue highlighted during early testing with the RSU software was the need to manually 

select a USB port for the transceiver operation. Instead of manually activating the USB port, this 

task should be performed automatically during software startup. 

The original RSUs were limited to 999 files to be acquired. With the upgraded triggering 

capabilities, it was desired to expand the number of files to 9,999. This accompanied the 

hardware modification of using a larger Micro-SD card. 

The original RSU software only allowed for downloads of raw data files. If there were a 
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thousand files on six or seven RSUs, downloading that amount of data would approach 

6 to7 GBs if the Micro-SD cards were nearly full. This would be a significant burden on the 

ISS’s down link bandwidth. A method was needed to download summary data that was a 

fraction of the total data but could provide ground personnel a way to prioritize the files that 

were required for download. 

In the first RSU software version, the operator set the operational steps and functions manually. 

For the type of testing that was being planned for the SDTO with the new triggering capabilities, 

manually setting the software was determined to be an unreasonable time burden for the ISS 

crew. This required the ability to upload a configuration file that would automatically set all of 

the parameters for a test or download. This configuration file could be written on ground and 

then uploaded to the ISS computer server so the ISS crew would only have to run the 

configuration file to start a test, download raw data, or download summary data. 

Finally, the project required an astronaut-friendly GUI. A GUI that had only a few buttons for 

the ISS crew to activate was needed. When activated, the crew would see a limited number of 

configuration files to choose from. Once selected, the desired configuration file would open and 

the selected operation would be implemented automatically. The selection buttons involved 

were: Verify/End Verify, which was used for verifying the RSU hardware during installation 

per a configuration file; Test/End Test, which started a series of data taking windows per a 

configuration file; Summary Download, which downloaded the specified summary files via a 

configuration file; Data Download, which downloaded the specified data event files via a 

configuration file; a Status query to update the GUI on the system’s status; and Erase, which 

allowed for the memory cards to be erased and reset. The Erase function was included in case 

there was a need to clear the memory card for more measurements, although it had the additional 

advantage of resetting a RSU in case a system malfunction occurred. In addition to operation of 

the SDTO functions, the GUI needed to provide the status of the various RSU functions. 

6.3 Proposed Certification Solutions 

Once the hardware/software/materials were delivered, the system had to undergo certification for 

flight. To minimize development costs, only the minimum safety certification tasks were 

proposed. An SDTO should represent a minimum level of ISS risk and those certifications 

required for that purpose had to be performed. Beyond that requirement, additional certifications 

related to environmental performance and launch survivability become trades between costs, 

schedule, and risks. These certifications included: EMI susceptibility; radiation susceptibility; 

electrical, electronic, and electromechanical (EEE) parts assessment; workmanship reviews; 

thermal testing; vibration testing; detailed hardware and software verification testing; and 

hardware and software integration testing. It was initially decided to focus on the certifications 

required for ISS safety and to accept the risks for the other certifications. During the 

development of the ISS CR to support the launch and implementation of the SDTO, it was 

advocated by the ISSP that, at a minimum, EMI susceptibility and radiation susceptibility testing 
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be included. The ISSP requested the EMI susceptibility testing to ensure that there were 

reasonable expectations that the wireless systems would function in the ISS environment. The 

ISSP was concerned about the issue of radiation susceptibility in part because the Micro-SD 

memory cards had no previous ISS history. If these devices should be susceptible to radiation 

effects, then this vulnerability could thwart data acquisition efforts. The ISSP felt the cost of the 

SDTO installation and operations was sufficient to justify verifying these issues in addition to the 

minimum ISS safety certifications. Finally, by meeting SSP 50835 requirements for 

certification, the RSU system could be launched on any vehicle traveling to the ISS. This 

reduced schedule risks by allowing the SDTO to launch on the next available vehicle traveling to 

the ISS. Meeting SSP 50835 requirements implies by internal references meeting all other 

necessary ISS certification documents. 

7.0 Implementation 

7.1 UBNT Hardware Modification Implementation 

7.1.1 RSU Transceiver Module 

The RSU transceiver modules (Figure 7.1-1 (a)) did not require hardware modifications. The 

USB cable that connected the transceiver modules to the SSC (Figure 7.1-1 (b)) was a 2.62 feet 

USB 2.0 cable. This cable incorporates a five-pin USB Mini-B connector (Figure 7.1-1 (c)) 

versus the more common four-pin Mini-B connector. In addition, this cable was wrapped with 

Teflon® tape as required for flight. 

 (a) (b) (c) 

Figure 7.1-1. (a) UBNT RSU Transceiver Module, (b) UBNT USB Cable with Velcro Cable Wrap, and 

(c) UBNT USB Connectors 
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7.1.2 RSU Sensor Module 

The RSUs were modified to allow the attachment of the L91 SSP Orbiter WLEIDS batteries and 

the attachment of an external antenna (Figures 7.1-2, 7.1-3, and 7.1-4). 

The NESC team calculated that two L91 batteries should be able to power a RSU to record and 

transmit approximately 10,000 event files. Each event file contains approximately 

65 kB of data. Laboratory testing using commercial (Li iron disulfide type AA) batteries 

succeeded in recording and transmitting over 13,000 files. During ISS use, it is expected that the 

number of files recorded and transmitted will be fewer than calculated and demonstrated during 

laboratory testing. The first reason is because of the battery de-rating as a result of the required 

certification testing. The second reason is that some power will be consumed while in standby 

mode for extended time periods. A program was implemented to track the power used during 

the UBNT SDTO so power management and reliable data scheduling can be performed. 

Figure 7.1-2. RSU Transceiver Module Modified for an External Battery (top right) and External 

Antenna Connection (top left) 
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Figure 7.1-3. SSP WLEIDS L91 Battery Pack with External Connection 

Figure 7.1-4. RSU Module with the WLEIDS L91 External Battery and 2-m External Antenna 

Initial external antenna functional testing was performed with a range of relative orientations and 

distances between the transceiver and the external antenna to develop guidelines for the antenna 

installation. It was determined the optimum antenna orientation was perpendicular to a wall. A 

mounting bracket was developed to orient the antenna in this configuration (Figure 7.1-4). A 

high fidelity functional test was also performed in the Node 2 mockup. The RSU was mounted 

on the Node 2’s pressure wall, while the antenna was installed in the corridor between two racks. 

Several relative transceiver and RSU antenna orientations were tested, which successfully 

demonstrated the RSU communications capability. 
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In addition, the Micro-SD card was changed to a 2 GB capacity. During functional testing, it 

was determined there were significant variations in the writing speed capabilities of Micro-SD 

cards from different manufacturers and manufacturing locations. When Micro-SD cards from 

different manufacturers were tested, it was found the Micro-SD cards from SanDisk® proved to 

be the most reliable in this application. It is believed that differences in data writing speeds 

caused the problems observed in initial testing in which some cards did not reliably store data 

from the system. These Micro-SD cards would hang-up during data transfer or, if writing the file 

took too long, the RSU software would change from trigger back to idle mode. Even with the 

SanDisk® Micro-SD cards chosen for flight, infrequently a specific Micro-SD card might not 

work reliably with a specific RSU. For that reason, additional functional testing was performed 

to verify that each Micro-SD card and each RSU worked together reliably. The testing involved 

writing 9,999 files onto each Micro-SD card to certify it for use with a specific RSU. These 

Micro-SD cards’ serial numbers were recorded so that they could be assigned to their 

corresponding RSU on orbit. 

Micro-SD card manufacturers are increasing card capacity while discontinuing cards with 

smaller memory. The 2 GB card size is at the limit of the RSU firmware’s ability. Therefore, 

improving the RSU data storage system by either modifying it to read larger Micro-SD sized 

cards or installing permanent memory is necessary. 

The final RSU modification involved increasing the system’s gain. Ground testing showed that 

the gains achieved were 27.8 dB at the low end of the sensor’s frequency range to about 25 dB at 

the upper end of the frequency range. Table 7.1-1 shows the modeled values of expected gains. 

The second column shows the ratio of the output to input, while the third column is the dB range 

of the second column. In addition, a test was performed with the transducers attached to a 

vibration table to measure the low frequency effects. Although these transducer elements are 

designed to work in a plate expansion mode and to operate from about 40 to 330 kHz, sometimes 

transducers show responses from unexpected modes at low frequencies. This could present an 

issue since structural vibration displacement amplitudes tend to be greater at lower frequencies. 

Hence, an unknown low frequency transducer response mode could lead to the capture of 

spurious large amplitude low frequency signals, which are not related to leak events. The RSU 

has a 1-kHz single pole, high-pass filter, so signals between 1 and 40 kHz were characterized to 

ensure that the system would be operated in the linear regime. Accelerometer testing on the ISS 

has measured 1 milli-g forces in the vicinity of 60 Hz, with the accelerations diminishing above 

approximately 200–500 Hz [ref. 4]. The results of the low frequency testing are shown in 

Figure 7.1-5, which shows there is an elevated sensitivity near 10 kHz, but it would require a 

0.1 g acceleration to approach RSU amplifier saturation. At 10 kHz, 0.1 g acceleration is not 

anticipated since above 500 Hz the measured accelerations were below 0.001 g and decrease in 

amplitude rapidly with higher frequency. Hence, low frequency effects are not expected to be an 

issue. 
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It should be reiterated that the DIDS was initially designed as an impact detection system. It was 

selected for the current application because it had capabilities and flexibilities that could meet the 

SDTO needs. Some of DIDS limitations (e.g., the system’s 10 μsec wake-up time from the idle 

to active data acquisition mode (to better identify a signals phase) and the analog front-end is 

limited to only a few sensor types) impact its possible usage for other applications, such as piezo 

polymer materials (piezo-patches), and these limitations could be addressed by further 

modifications. Shorter activation times would allow the system to capture faster events without 

the interference of transient waveforms inherent in the data acquisition electronics. 

Table 7.1-1. Gain/Frequency Values Model for the RSU Sensor Modules 

Freq (kHz) Gain (Vout/Vin) Gain, dB 

10 24.6 27.82

20 24.8 27.89

50 24.7 27.85

100 24 27.60

200 22 26.85

300 19.6 25.85

400 17.2 24.71

500 15.4 23.75

600 13.6 22.67

700 12 21.58

800 11.1 20.91

900 10 20.00

1000 9.1 19.18
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Figure 7.1-5. RSU Low Frequency Response Connected to the B225.5 Sensors after 10 milli-g 

Acceleration Excitation 

This may help to reduce power consumption when capturing either fast or slow events because 

the sensor unit can wake up, gather data, and shut down faster (i.e., operate in the higher-power 

mode for less time). Improvements to the analog front-end to increase the unit flexibility for 

other applications could enable the use of additional types of transducers without having to use 

haywires. It could provide for better filtering and clamping for other types of transducers 

(e.g., piezo-patch transducers). 

7.1.3 RTV142 Adhesive 

In order to detect acoustic signals through the wall structure, adequate acoustic coupling between 

the transducer and the pressure wall is required. However, for this SDTO, a temporary 

transducer installation was required that would not damage the wall or leave residue. The 

approach developed was to first place a thin layer of Kapton® tape on a clean area of the pressure 

wall structure and then to adhesively bond the sensor to the tape. In laboratory tests, the thin 

layer of tape did not produce a measurable effect with this instrumentation. This approach has 

been successfully used for ground-based tests on SSP and ISS structural components. Kapton® 

tape was selected based on its approved use on the ISS and it does not leave adhesive residue. 

Materials and Processing personnel at JSC suggested that RTV142 be used to bond the sensor to 
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the tape. This RTV has a low VOC rating during the 4-hour cure, which made it more attractive 

than most adhesives for use on the ISS. 

To control the amount of adhesive that was used for each bond and to simplify the installation 

procedure for the astronaut, a syringe-dispensing system was utilized. Figures 7.1-6 and 7.1-7 

show the syringe dispenser and the syringe filled with RTV142, respectively. Removal of the 

transducer involved twisting the sensor to break this adhesive bond and then removing the tape. 

Timed installation tests in the Node 2 mockup indicated that one crew member could mount and 

verify the hardware system with four transducers behind a rack bay in less than 

25 minutes.

Figure 7.1-6. RTV Syringe Dispenser 

Figure 7.1-7. RTV Loaded Syringe 

7.2 UBNT Software Modification Implementation 

The UBNT software application is entitled DIDSFlight.exe. This software application will be 

loaded on an ISS server. Any ISS SSC will be able to install and operate the software by 

locating and then activating the installer. 

7.2.1 RSU Flight Control Software GUI 

It was decided early in the investigation to update the software’s GUI to simplify ISS crew 

operations. Figure 7.2-1 shows the RSU Flight Control Software GUI. There are two major 

functions visible in the streamlined GUI: the Commands and the RSU sections. The Command

section consists of eight buttons for operating the UBNT. The RSU section shows the sensor 
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status. The original RSU software had numerous buttons that opened pull down menus that 

provided various options and steps that required activation or selection to start RSU testing. 

Figure 7.2-1. RSU Flight Control Software GUI 

Under the Command section, the Request Status button will command selected RSUs to return 

their status information. The Verify button will put selected RSUs into the threshold trigger 

mode. Using this operation, the ISS crew can show that the system is operating properly by 

manually triggering the transducers. The crew will perform this function only during sensor 

installation. The End Verify button will change the RSUs from the trigger mode to the idle 

mode. The Test button will program selected RSUs into scheduled trigger mode for performing 

data acquisition. Once activated, the RSUs will run independent of the computer system and will 

perform their scheduled data acquisition without further computer control. The End Test button 

will allow the crew to stop the operations of the selected RSUs and return them to idle mode. 

The Download Summary button will allow summary data to be downloaded to a SSC. This 

data will be down linked for initial data analysis. The Download Data button will allow 

selected event data files to be downloaded to a SSC for subsequent down link to ground for 

detailed analysis. The Erase SD Card button will allow the crew to erase the memory card. 

Most commands will execute within a few seconds, while select commands (e.g., Download 

Data) may take a significant amount of time depending on the amount of data requested. When 

any of these Command buttons is activated, smaller status dialog windows will appear to 

indicate the command status as the communications with the RSUs are progressing. When the 

command is complete, the status dialog window will automatically disappear. 

Under the RSU section, the status of various modes and systems are displayed for the listed 

RSUs. The RSU section’s first column refers to the RSU’s serial numbers, which is how 
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specific RSUs are addressed. The second column refers to a Description, which supplies 

information about the test or operations underway, and will be included in the data file header for 

future reference. The Sensor Type will always be listed as Acoustic Emission for this UBNT 

SDTO since the amplifier’s impedance was set up only for Acoustic Emission sensor types. The 

fourth column shows the RSUs Mode, which refers to whether the RSU is idle, in trigger mode 

(threshold trigger), or in scheduled trigger mode (programmed schedule trigger). The Idle Rate

column indicates how frequently (in seconds) the RSUs will be checking RF communications. 

The Memory Free column shows the available memory (MB) on the Micro-SD card. The 

Battery column gives a measure of the battery voltage (volts), which can be an indication of the 

remaining battery life. The Temperature column indicates the RSU temperature (°C). The 

Signal column indicates how strong (dBm) of a communication link signal has been detected. 

The RTC Time is a date and time stamp indicating the latest event’s date and time. Certain 

operations (Verify, Test, Erase SD Card) will reset the time to the current SSC time. The File 

Number indicates the number of files that a RSU has written on the Micro-SD card. 

7.2.2 Automatic Communications with the Transceiver 

In earlier RSU software versions, once the software was activated, the user first needed to 

manually determine which USB port was being used and then activate the port from the 

software. In the current version, when the software is activated, it automatically searches the 

USB ports to determine which one is connected to the transceiver unit. If the transceiver is not 

connected, then an error message will be displayed. Connecting the transceiver will clear this 

error message. If the transceiver is correctly connected, then the USB port number will be 

displayed at the bottom left side of the application’s status bar for quick reference and 

verification that the transceiver is operating. If the transceiver should be disconnected at some 

point during testing, then reconnecting the transceiver will automatically allow the software to 

relocate the correct USB port for proper communications. 

7.2.3 Verify Operations 

On orbit, qualitative verification of the RSUs, transceivers, and transducer operation is 

performed by exciting the transducers with a signal produced by physically tapping the sensing 

face with a hard object. The resultant signal causes the RSU to trigger and record a signal, which 

can then be transmitted to the computer. This verifies: the transducer can produce an adequate 

signal to trigger the RSU, the RSU can successfully record data, and the RF communications are 

working. A controlled input signal, not available on ISS, is required to perform a quantitative 

assessment of the transducer and system’s response. Plus, the availability of an astronaut’s time 

to do additional verification testing steps is very limited. For these reasons, in this SDTO, it is 

assumed that if the system is operational, then it is performing as calibrated on the ground. 

Activation of the Verify command will allow the ISS crew to set RSUs into the trigger mode. 

After selecting the Verify button, an open file dialog window will be available to select a RSU 
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Configuration file. The RSU Configuration files contain the programming information for 

setting up the RSU. These files will be written on the ground and uploaded to the SSC for crew 

selection. Once selected, the RSUs will be displayed in the Remote Sensor Units section and a 

RSU Status dialog window will be opened to provide the operation status during setup. The 

command includes three operations: Set RTC, Program acquisition setup, and Set trigger mode. 

This last operation includes setting the idle rate. 

The Verify operation can be terminated by selection of the End Verify button. This command 

sets the RSUs listed in the Remote Sensor Units section back to idle mode. If the RSU list is 

empty, then an open file dialog will be available to select a RSU Configuration file. Again, a 

RSU Status dialog will appear to provide the system operation status being placed into idle 

mode. 

7.2.4 Test Operations 

This command programs the RSUs into the schedule mode. The original DIDS units did not 

support this function. Background noise measurements are required when the environment is 

quiescent and active (i.e., quiet and noisy). For that purpose, threshold triggering is inadequate. 

If the environment is quiet, then the RSU units will not trigger because the trigger threshold 

signal will be too low. If the threshold trigger level is set very low, then when the environment 

becomes noisy, the RSU units will start to trigger too often, causing an overflow of data. 

The Schedule mode provides a rudimentary level of control that is sufficiently flexible to capture 

the background noise levels by targeting ISS operational phases. The system allows up to 

sixteen data acquisition windows to be set. The data acquisition windows are setup by 

specifying the start time (date and time) and the window’s duration (from 3 to 255 minutes, in 

one minute units). During a data acquisition window, the frequency of triggering can be set 

between 15 to 127 seconds per trigger. The fastest rate of 15 seconds/trigger is an approximate 

limitation of the RSU’s ability to record and store data, and then to reset itself for the next event. 

The concept is to be able to plan data acquisition windows during planned ISS operations. 

However, the system could be set to record events throughout a day on a nearly continuous basis 

if desired. The system allows the RSU to be in both a scheduled and a threshold trigger mode 

simultaneously, in case the operator wants to try to capture loud events while recording on a 

regular schedule. Testing under the dual trigger mode did indicate data recording errors 

suggesting triggering collisions between the synchronous and asynchronous triggers. Therefore, 

dual trigger mode will not be used for this SDTO. 

Selecting the Test button will open a file dialog box, which will allow selection of a Test 

Configuration file. The Test Configuration files will contain the programming information for 

setting the RSUs for data acquisition. The Test Configuration files will be written on the 

ground and uploaded to the SSC for crew selection. If a Test Configuration file is not uploaded 

in advance of a specific test or the crew cannot start a test by the appropriate time, then a 

software filter compares programmed data acquisition window times with the SSC clock. The 
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Test Configuration file will be processed appropriately to avoid missed windows and allow 

remaining windows to be processed. Once selected, the RSUs will be displayed in the Remote 

Sensor Units section and a RSU Status dialog will be shown to provide the operation status 

during programming. The command includes four operations: Set RTC, Program acquisition 

setup, Set idle rate, and Set schedule. Once the programming operations are completed, the 

RSUs should be in the scheduled mode ready to acquire data. At this point, the SSC is not 

required for the RSUs to function. If the GUI is turned off and restarted, then a Request Status

command will be necessary to update the Remote Sensor Units section to obtain the latest status 

information. 

If the ISS crew should need to terminate a test operation, they can implement the End Test

command to set all RSUs listed in the Remote Sensor Units section to the idle mode. After 

selecting the End Test button, a RSU Status dialog window will appear providing the operation 

status. The status dialog will automatically close upon completion. 

7.2.5 Data Downloading Operations 

The original RSUs only provided for downloading raw data. One method of data transfer from 

the RSUs to a computer is to remove the Micro-SD card and install it into a computer card 

reader. This can be accomplished if the RSU units are readily accessible. However, if the RSU 

units are behind ISS equipment racks, then this method of data transfer is impractical. The other 

process for downloading data requires transfer via RF link, which has the disadvantages of 

limited transfer rates and battery power usage. With optimal RF communications and sufficient 

battery power, the transfer time for a file was measured to be approximately 12 seconds. One 

RSU unit with 1,000 files would require between 3 to 4 hours to transfer files, which would 

consume a significant amount of battery power. Multiplying that time by six or seven RSUs as 

proposed in this investigation, means the total data download would take more than a day’s time. 

It is expected that more than 1,000 data files per RSU unit will be acquired in this SDTO, so the 

time impact would be greater. The download process does not require ISS crew oversight, but it 

would require a computer to be operational during that time. Furthermore, it is not expected that 

all of the data acquired will be of immediate interest. Only a fraction of the data will be required 

to obtain an understanding of the ISS background noise levels. However, it is not known a priori 

at which instances the important data will occur, so the system will be required to be 

programmed to record substantial amounts of data to capture the few important times when the 

noise levels are at their maximum. 

To address these data constraints, it was decided to emulate the process used by the SSP Orbiter 

WLEIDS. The WLEIDS system records data continuously for a number of minutes starting with 

launch and running until the external tank has been jettisoned. The goal is to detect impact 

signals that are only a few milliseconds in duration. The system captures several gigabytes of 

data during launch and ascent, yet the SSP Orbiter’s downlink capabilities are limited. Hence, a 

system was developed to download summary files that are only a few kilobytes of data. Based 
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on the summary file review, the complete time history data for only a few larger amplitude 

signals of interest are downloaded and reviewed for possible impact signals. 

The RSU firmware was modified to write both a data file and a data summary file for each event. 

A data file is approximately 65 kB, while the summary file is only a few bytes containing header 

information including the Peak and the RMS values for the four recorded RSU channels. The 

GUI has a command button to download the summary data. Once activated an open file dialog 

window will be available to select a RSU Download Summary List, which will have been 

uplinked to the ISS. Once selected, the RSUs will be displayed in the RSU list and the RSU 

Status dialog will display the operation status. The command includes three operations: Request 

Status, Request Configuration, and Download. The system will download a summary file for 

each file requested in the Summary Configuration File. Once downloaded to a SSC, the 

software will write a single file with tabulated summary data from each RSU. In addition, a 

Download List Extensible Markup Language (XML) file with all file numbers listed in the 

Summary Combined file will be generated for each RSU. The Download List XML file can be 

modified into a Download Data Configuration file specifying the specific data files to be 

downloaded. This process simplifies the programming of a Download Data Configuration file. 

Both the Summary Combined file and the Download List XML file will be down linked for 

evaluation and development of the Download List Configuration file that will need to be 

uplinked to the ISS. 

The Download Data command will download the requested event files. Once the Download 

Data button is activated, an open file dialog window will be available to select a RSU Download 

List Configuration file. Once selected, the RSUs will be displayed in the RSU list and the RSU 

Status dialog window will be shown to provide the operation status. The status dialog window 

will show how much time has been spent on downloading each RSU. The downloaded files can 

be converted to engineering units and exported to comma-separated values (CSV) text files. The 

raw data files will be down linked for processing. During downloading of summary data and 

event data, the RSU activity and error log files will be down linked for review, if desired.

7.2.6 Memory Management 

The original RSUs only allowed for 999 files to be written to the Micro-SD card. The limitation 

exists due to a file naming limitation of 8 characters per file name. As five of the characters 

were dedicated to the RSU serial number naming convention, only three characters were 

available for numbering. This feature was modified to allow for four characters to be used for 

numbering, allowing 9,999 files to be written. This new feature required that the Micro-SD card 

to be increased to 1 GB or larger. The firmware had an upper limitation on the addressable 

memory size of 2 GB. Since memory card sizes have been increasing, it is becoming difficult to 

find the smaller memory cards, so it was decided to certify the usage of 2 GB cards. The 

operational impact is that the files now require more time to write than they did for the original 

250 MB cards. The original speed for recording a file was approximately 5 seconds to record, 
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store, and reset the RSU. Now the approximate recording cycle time is approximately 

12 seconds. 

It should be emphasized that there is no data backup for the current configuration. Only the data 

that is down linked will be backed up. Once data is down linked, the files on the SSC will be 

purged. A second set of Micro-SD cards was included in the SDTO package to provide 

contingency for extra memory. The plan is to trade the Micro-SD cards with spares in between 

the transition from setup in the Node 3 to the US Laboratory to help ensure that the data 

requirements on orbit are not exceeded during the SDTO operations. It is desired to recover 

these Micro-SD cards, which is difficult in the present space flight system environment 

(i.e., limited down mass opportunities). 

Given the limited memory options, it was decided that the erase files command should be made 

available to the ISS crew in case it became necessary to clear the memory during this SDTO. 

This operation allows commanding units that are in the idle mode to: erase all files, format the 

memory cards, perform a reset, and return their status information. After selecting the Erase SD 

Card button, an open file dialog window will be available to select a RSU Configuration file. 

After a file is selected, the RSUs and a warning dialog will be displayed requesting confirmation 

that the Erase SD Card action is intended. If the crew decides to proceed, the RSU Status dialog 

will provide the operation status. Set RTC and Set idle rate will be performed immediately after 

the data is erased and reset performed on the units. When the operation completes, Idle Rate, 

Memory Free, RTC Time, and File Number columns will be updated to match the RSU status. 

The File Number will be zero for units that are in the idle mode. 

While these software modifications have greatly increased the RSU capabilities, there are several 

software and firmware issues that should be highlighted. First, the RSU program memory for the 

internal operation of the sensor units has reached its limitations. No additional algorithms can be 

added without deleting or losing other capabilities. Secondly, the system does not fully 

implement automated command file processing. The utilized operational method simplifies the 

operations the ISS crew must implement, but the system does not allow fully autonomous 

operation. Crew action is required to start and stop the software. This capability exists in other 

Invocon, Inc. systems (e.g., the SSP WLEIDS and the External Wireless Instrumentation System 

(EWIS)). Fully automated command file processing would enable the ground to perform system 

operations remotely. Third, the data file lengths are fixed. There may be other applications 

where having flexibility in the recorded data lengths might be required. The EWIS and Internal 

Wireless Instrumentation System (IWISTM) that are on ISS have this capability. If the RSU had 

the ability to continuously write data to non-volatile memory, then it would significantly expand 

the applications for which a RSU could be used. Presently, each acquisition is 8,192 samples 

long. In many cases, longer acquisitions are desired or required. Adding this capability would 

be primarily focused on upgrading the field-programmable gate array code with the result that 

data could be continuously streamed to the SD card until the available memory is depleted. 
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Finally, with regard to the use of the DIDS for an impact detection system, it should be reiterated 

from the NESC report [ref. 2] that two features impact the accuracy and ease of use. One issue is 

the poor internode synchronization between DIDS units. For this investigation, that is not an 

issue, as the sensors are synchronized before each test, but it does become an issue for long 

testing or sensing operations (i.e., waiting for days for an impact signal). Once set up, these units 

are autonomous from each other so that if the timing of one unit drifts with respect to a second 

unit, data correction cannot occur. Modifying the RSU by refining the internode synchronization 

would enable multiple sensor units to be synchronized based on when they are triggered via an 

input waveform. This is useful for integrating and analyzing a signal covered by multiple sensor 

units. Secondly, for purposes of impact location, it would be helpful if the software could 

identify the triggering channel. This is not an issue that affects this SDTO effort.

7.3 UBNT Certification 

7.3.1 Requirements 

In 2008, the ISSP developed SSP 50835, which outlined the requirements for payload to be 

launched on any ISS-approved vehicle. It was decided to certify the equipment for this SDTO to 

these requirements. By increasing launch flexibility, the SDTO’s schedule risks were reduced. 

Another benefit for meeting SSP 50835 requirements is that it would help simplify possible 

future development and certification of a leak location system that might be based on this type of 

hardware. Meeting SSP 50835 requirements implies by internal references meeting the 

necessary ISS certification documents. 

The initial target vehicle was the SSP flight STS-134, which was initially scheduled for launch in 

the second half of February 2011. To launch on that flight, this SDTO package needed to be 

completed with the required certifications approved and shipped to KSC by December 19, 2010. 

By October 2010 this SDTO had secured a place on the payload manifest for STS-134, but this 

activity was not listed as a high priority payload compared to other manifested hardware. An 

opportunity to be included as a late load on ESA’s ATV-2 vehicle was identified as an alternate 

launch vehicle. The schedule requirement for launch on the ATV-2 flight was to have the 

hardware and required certifications approved and shipped to KSC by December 10, 2010. The 

team shipped the SDTO package on November 26, 2010, and obtained the final approval on the 

certification documents on December 6, 2010. At KSC, a Preship Review was completed and 

the SDTO package was then delivered to the Arianespace’s Spaceport in Kourou, French Guiana 

on January 6, 2011, for integration onto ATV-2. 

An SDTO should represent a minimum level of risk to the ISS and those certifications required 

for that purpose are mandatory for completion. Beyond these ISS safety certifications, additional 

certifications became a trade between cost, schedule, and performance risks. To minimize 

development costs, only the minimum certification tasks were proposed. It was initially decided 

to focus on the certifications required for ISS safety and to accept the risks of not performing 
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additional certifications. Formal reviews (e.g., Preliminary Design Review, Critical Design 

Review and System Test Review) and certifications (e.g., EMI susceptibility and radiation 

susceptibility, thermal and vibration testing, comprehensive hardware and software verification 

and integration testing, and EEE parts reviews) are significant cost drivers. During the 

development of the ISS CR 012334, it was directed by the ISSP that EMI susceptibility and 

radiation susceptibility testing should be included. The ISSP requested the EMI susceptibility 

testing to ensure that there were reasonable expectations the wireless systems would function in 

the ISS environment. The ISSP was concerned about the issue of radiation susceptibility in part 

because the RSU Micro-SD memory cards had no previous ISS use history. If they were 

susceptible to radiation effects, this could prevent acquisition of data. The ISSP felt the cost of 

the SDTO installation and operations was sufficient to justify verifying these two issues in 

addition to the originally proposed SDTO safety certifications. 

7.3.2 Certification Testing 

To meet the flight deadline schedule, efforts were made to perform certification testing in 

parallel with the system modifications being performed. Items, such as the WLEIDS L91 battery 

packs, which were already available and were certified for the SSP, had their certification 

documents adapted or converted to ISS certification documents where possible. The L91 battery 

packs were modified by having an additional Nomex® covering, which caused the battery packs 

to require recertification for off gas products. 

Materials such as the RTV142 adhesive started undergoing certification immediately. The 

Toxicology group at JSC issued a report on the RTV142 offgas products [ref. 5]. Testing 

showed that 454 mg of RTV142 produced 1.2 mg of methanol or propylene glycol and 

9.8 mg of siloxanes during the first 24 hours. After 9 days, additional siloxanes were emitted for 

a total of 21 mg. The generation of all alcohols is regulated on the ISS because of their 

deleterious effects on filters in the Water Processing Assembly (WPA). Therefore, a VOC 

Usage Agreement (VUA) was required [ref. 6]. The agreement required that the SDTO would 

not release more than 10 mg/day. This equated to the installation of about 14 transducers per day 

maximum. The toxicology report indicated that the level of siloxanes would not present any 

problems provided the SDTO did not exceed more than 300 transducer bonds per 6-month 

increments on the ISS. As this SDTO only planned to make 52 bonds total, this limit will not be 

violated. 

To start the certification process, Invocon, Inc. agreed to deliver two RSUs with the required 

hardware modifications (but lacking software modifications) as early as possible. Those units 

were used to begin off gas and EMI testing. The off gas testing was performed at the JSC-White 

Sands Test Facility (WSTF) at the end of August 2010. The testing involved a RSU, including 

RSU sensor unit, transceiver, transducers (4), transducer cables (4), antenna extension cable, 

antenna mount, USB data cable, battery pack, Micro-SD card, and adhesive syringe dispenser. 

As mentioned previously, at this time a separate offgas test was also performed on the battery 
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pack, which addressed the addition of Nomex® among other issues. The UBNT kits passed this 

test. The Toxicology group at JSC issued a toxicology assessment memorandum for the 

Energizer® L91 Li iron disulfide batteries [ref. 7]. 

EMI testing began in early August 2010. The test involved a RSU, including RSU sensor unit, 

transceiver, transducer, transducer cable, antenna extension cable, antenna mount, USB data 

cable, battery pack, and a 1 GB Micro-SD Card. The emission tests spanned frequencies from 

14 kHz through 10 GHz. Results [ref. 4] are presented in graphical form in Figure 7.3-1. The 

RSU emissions threshold limitations are indicated in the graph showing that the hardware fails 

the EMI test at about three frequencies near 100 kHz. It was reported that these failures did not 

cause concern because there were no receivers at these frequencies on ISS [ref. 8]. A Radio 

Frequency Authorization Report and a Tailoring Interpretation Agreement (TIA) [refs. 9, 10] 

were generated as required from the Station Electromagnetic Effect Board (SEEB) to approve 

these exceedances. With respect to susceptibility testing, there were several frequencies where 

the RSU failed the EMI susceptibility testing [ref. 4]. These frequencies are where known 

transmitter frequencies exist on ISS and from other space vehicles that might operate nearby, 

which could be a concern. These issues would be mitigated if the RSUs were to have a metallic 

enclosure rather than the Delrin® case. 

At the point of this testing, resources and time were not available to modify the enclosure, so the 

investigation pursued other means to mitigate those risks. The method to mitigate the risks will 

be via procedure changes. For example, the RSUs use the same communication frequency as the 

ISS IWISTM. While the communication links are coded, the IWISTM is a more powerful 

transmitter so it could interfere with the RSU. In this case, a procedure was established to ensure 

the two systems do not operate at the same time, avoiding the potential conflict. A similar 

process will be applied to other frequency conflicts to limit the risks. 

After the EMI testing was completed, it was determined there was a need to change the 

Micro-SD card capacity from 1 to 2 GB, and to switch manufacturers to obtain better quality 

cards. For that hardware change, an assessment of similarity certification was performed. The 

USB cable was verified for continuity, dielectric withstanding voltage, and insulation resistance. 

A de-rating analysis of the circuit protection devices of the WLEIDS L91 battery pack was 

performed and the equipment passed that analysis. 
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Figure 7.3-1. EMI Test Results 

A thermal analysis memorandum was generated for the UBNT [ref. 11]. Each of the UBNT 

system’s components was assessed for strength, fracture, and venting and all parts were 

classified as non-fracture critical and safe to venting hazards. A Materials and Fracture Control 

Certificate was issued for the UBNT [ref. 12]. 

Radiation testing was performed on August 31, 2010, at the Indiana University Cyclotron 

Facility [ref. 13]. The Micro-SD cards and a RSU with a transducer were tested in both static 

and dynamic operating modes. The proton radiation levels were in excess of 600 rads. Three 

Micro-SD cards tested suffered fatal destructive errors during the dynamic testing. The rate of 

failure indicated that the MTBF ranged from 54.6 to 473 days for that test condition. The RSUs 

with an attached transducer suffered a single functional interrupt during its testing. Power 

recycling the RSU allowed the unit to recover normal operations. The estimated MTBF was 

1,790 days. Both of these system failures appeared to occur during dynamic operational states. 

When the unit was in idle mode or when the Micro-SD cards were in a static state, they did not 

appear to suffer failures. It was only when the components were undergoing dynamic operations 

that failure occurred. Since the RSUs will generally be quiescent during most of their 

installation time, it is expected that the effective MTBF will be an order of magnitude greater. 

Therefore, it is expected the radiation susceptibility risks are low. Finally, a UBNT Safety Data 

Package was generated and approved and a Flight Safety Certificate was signed [refs. 14, 15]. 
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7.3.3 Functional Testing 

With the hardware delivery, functional testing was undertaken to evaluate the hardware and 

software performance. In total, nine RSUs required testing. Only seven systems were going to 

be launched. The other two systems were to be used for ISS crew training and ground support 

testing as required. It was determined that these functional test results would be used to 

determine which units were to be for ground support. 

Prior to delivery, Invocon, Inc. measured the energy used by the nine RSUs. The units were 

essentially identical in their battery power drain except RSU 1001. This unit was one of the first 

two units purchased and had an idle current drain that was about twice what the other eight units 

experienced. As battery maintenance is an operational issue, RSU 1001 was assigned to ground 

support. 

For functional testing, a continuous signal from a signal generator was input into the RSUs. Test 

Configuration files were written to configure the systems to operate in a programmed schedule 

mode and in simultaneous programmed, scheduled, and threshold-triggered modes. In all, the 

systems were configured to record 9,999 event files. 

Invocon, Inc. reported that during software functional testing prior to delivery, errors had been 

observed. With the infrequency of the faults, it was difficult to determine their origin. In all, 

there appeared to be three distinct types of errors that occurred. One error type was manifested 

by the RSU unit locking up. The system could download data and be programmed, but when it 

was set to acquire data, it would drop back into idle mode. The unit would not record additional 

data until the memory card was erased. A second error type involved one of the RSU channels 

to become unresponsive, recording zeros instead of signals, while the other three channels 

functioned properly. This error would persist until the power was cycled. The third error type 

occurred when an event was triggered, but all the channels read zero. The unit would recover on 

the next trigger. This error only occurred when the systems were operated simultaneously in the 

scheduled and triggered modes. This error did not appear when the systems were operated in the 

scheduled mode only. 

It was suggested that the first error type might be related to a Micro-SD card interaction with the 

RSU unit. This type of error appeared to occur more frequently with the poorer quality MicroSD cards that were first tried and was part of the justification for switching to the final model of 

memory card. As part of a method to mitigate this error, all the Micro-SD cards were tested and 

the RSU unit they were tested with was documented. It was decided that any case of this first 

type of failure would result in that Micro-SD card being discarded. Furthermore, during the 

SDTO, the Micro-SD cards are only to be used with the RSU units in which they had been 

successfully tested. It is hoped that this procedure will eliminate the source of the problem 

causing the first type of error. If it did not, then at least the data could be downloaded and the 

memory card could be reset bringing the system back to a functioning state. 

If the second type of error occurs during the SDTO, it is not considered to be fatal to the testing. 
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Typically, each RSU is to have all four channels connected to installed transducers. This would 

provide some redundancy so that if one of the channels was to fail, there will be three other 

transducers that could record significant signals. 

The third type of error seemed to be associated with a conflict between scheduled and threshold 

based triggering modes. If that is correct, then it can be avoided by recording in the scheduled 

mode only. Initially, it was felt that there might be situations where being able to record a 

random loud signal while recording the regularly scheduled signals might provide the most 

complete set of information. However, it is anticipated that recording data in the scheduled 

mode for long enough time periods should provide satisfactory data to bound the noise 

environment. 

During this functional testing, one of the units (RSU 1034) experienced two instances of errors 

of the first type. The first time, the error occurred after 7,701 events were recorded, and the 

second time was after 7,837 events were recorded with the same Micro-SD card. It was decided 

to use this RSU as the second unit for ground support. 

7.3.4 Documentation 

Figure 7.3-2 shows the UBNT Drawing Tree for the hardware and the corresponding drawings.

Figure 7.3-2. UBNT Drawing Tree 

 

The following documents are the certification documents referenced for this SDTO: 
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1. Energizer Lithium L91 Application Manual [ref. 22] 

2. L91 Energizer Material Safety Data Sheet (MSDS) Document [ref. 23] 

3. RTV 142 Off gas Products Memorandum [ref. 5] 

4. RTV142 MSDS Document [ref. 24] 

5. Volatile Organic Compound Usage Agreement [ref. 6]

6. Materials Test Data Transmittal Memorandum [ref. 25] 

7. Offgas Test Report, WSTF [ref. 17] 

8. Toxicology Assessment for Energizer Iron Memorandum [ref. 7] 

9. Certification Test Report: Electromagnetic Interference (EMI) for the Ultrasonic 

Background Noise Test (UBNT) [ref. 8] 

10. Certification of Similarity for Use of an Upgraded Micro-SD Memory Card in Hardware 

Supporting Ultrasonic Background Noise Tests (UBNT) Memorandum [ref. 18] 

11. JSC Radio Frequency Authorization [ref. 9] 

12. ISS Electromagnetic Effects Panel Tailoring/Interpretation Agreement [ref. 10] 

13. Screening Report Electrical Harness Testing [ref. 19] 

14. Derating Analysis of Circuit Protection Devices of Ultrasonic Background Noise Test 

Memorandum [ref. 20] 

15. Thermal Analysis of Ultrasonic Background Noise Tests Components Memorandum 

[ref. 11] 

16. Strength, Fracture, and Venting Assessment of Ultrasonic Background Noise Tests 

(UBNT) Assembly Kit Memorandum [ref. 16] 

17. JSC Materials and Fracture Control Certification Memorandum [ref. 12] 

18. EP5 Battery Design Evaluation Form [ref. 21] 

19. Radiation Test Report Invocon Sensor and Micro-SD Cards [ref. 13] 

20. Station Development Test Objective Safety Data package for the Ultrasonic Background 

Noise Test (UBNT) [ref. 14] 

21. Flight Safety Certificate [ref. 15] 
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8.0 Findings, Observation, and NESC Recommendations 

8.1 Findings 

The following NESC team findings were identified: 

F-1. The RSU hardware and software necessary to perform an SDTO to characterize the 

ultrasonic background noise on the ISS was successfully acquired, modified, tested, and 

certified for use on the ISS. 

F-2. There is a lack of instrumentation that can provide a controlled input signal that can 

perform a quantitative assessment of the transducer and system’s response on orbit. 

F-3. During certification testing, the RSUs did not fully pass the EMI emissions and 

susceptibility testing but were deemed acceptable as a SDTO. 

F-4. The 2 GB Micro-SD cards demonstrated radiation susceptibility during dynamic testing 

that translated into a MTBF of 54.6 to 473 days. 

F-5. The Micro-SD cards are a pending RSU weak link as the 2 GB storage size will soon 

become obsolete. In addition, it is noted that the RSU in its current configuration has 

reached numerous software, firmware, hardware, and operational limitations.

8.2 Observation 

The following NESC team observation was identified: 

O-1. Requests to utilize RSUs to support other NASA testing (e.g., composite overwrap 

pressure vessels (COPVs) at WSTF and Bigelow’s inflatable habitat module) could not 

be supported.

8.3 NESC Recommendations 

The following NESC team recommendations were identified: 

R-1. The ISSP should complete the SDTO Phase I data acquisition and analysis, and plan for a 

Phase II effort to the international partner modules. (F-1) 

R-2. The ISSP should assess the results of this SDTO to determine the ability to detect and 

locate leaks and predict damage locations. (F-1) 

R-3. The ISSP, in preparation for leak location or impact detection operations, should plan to 

develop a quantitative method and instrumentation to verify system operation while on 

orbit. (F-2) 

R-4. Future NASA RSU acquisitions that utilize the external antenna should be made with a 

metal enclosure to provide EMI and radiation shielding. (F-3 and F-4)
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R-5. The NASA Program offices should continue RSU improvements to address the MicroSD card obsolescence and operational/functional flexibility to support their program 

needs. (F-5)

9.0 Alternate Viewpoints 

There were no alternate viewpoints. 

10.0 Other Deliverables 

There were no other deliverables. 

11.0 Lessons Learned 

There were no lessons learned. 

12.0 Definition of Terms 

Corrective Actions Changes to design processes, work instructions, workmanship practices, 

training, inspections, tests, procedures, specifications, drawings, tools, 

equipment, facilities, resources, or material that result in preventing, 

minimizing, or limiting the potential for recurrence of a problem. 

Finding A conclusion based on facts established by the investigating authority. 

Lessons Learned Knowledge or understanding gained by experience. The experience may 

be positive, as in a successful test or mission, or negative, as in a mishap 

or failure. A lesson must be significant in that it has real or assumed 

impact on operations; valid in that it is factually and technically correct; 

and applicable in that it identifies a specific design, process, or decision 

that reduces or limits the potential for failures and mishaps, or reinforces a 

positive result. 

Observation A factor, event, or circumstance identified during the assessment that did 

not contribute to the problem, but if left uncorrected has the potential to 

cause a mishap, injury, or increase the severity should a mishap occur. 

Alternatively, an observation could be a positive acknowledgement of a 

Center/Program/Project/Organization’s operational structure, tools, and/or 

support provided. 

Problem The subject of the independent technical assessment/inspection. 

Proximate Cause The event(s) that occurred, including any condition(s) that existed 
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immediately before the undesired outcome, directly resulted in its 

occurrence and, if eliminated or modified, would have prevented the 

undesired outcome. 

Recommendation An action identified by the assessment team to correct a root cause or 

deficiency identified during the investigation. The recommendations may 

be used by the responsible Center/Program/Project/Organization in the 

preparation of a corrective action plan. 

Root Cause One of multiple factors (events, conditions, or organizational factors) that 

contributed to or created the proximate cause and subsequent undesired 

outcome and, if eliminated or modified, would have prevented the 

undesired outcome. Typically, multiple root causes contribute to an 

undesired outcome. 

13.0 Acronyms List 

ATK Alliant Techsystems, Inc. 

ATV-2 Automated Transfer Vehicle-2 

CIRD Common Interface Requirements Document 

COPV Composite Overwrapped Pressure Vessel 

CR Change Request 

CSV Comma Separated Values 

dB Decibel 

DIDS Distributed Impact Detection System 

EEE Electrical, Electronic and Electromechanical 

EMI Electromagnetic Interference 

ESA European Space Agency 

ESMD Exploration Systems Mission Directorate 

EWIS External Wireless Instrumentation System 

FSSB Flight Software Systems Branch 

GB Gigabytes 

GFE Government Furnished Equipment 

GHz Gigahertz 

GUI Graphical User Interface 

Hz Hertz 

IRMA ISS Risk Management Application 

ISS International Space Station 

ISSP International Space Station Program 

IVHM Integrated Vehicle Health Monitoring 

IWISTM ISS Wireless Instrumentation System 
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00629

Version:

1.0 

Title: 

Development and Certification of Ultrasonic Background Noise 

Test (UBNT) System for use on the International Space Station 

(ISS)

Page #:

42 of 45

NESC Request No.: TI-10-00629 

JSC Johnson Space Center 

kB Kilobyte 

kHz Kilohertz 

KSC Kennedy Space Center 

LaRC Langley Research Center 

Li Lithium 

MB Megabytes 

mg Milligrams 

MHz Megahertz 

milli-g 1/1000 of the Gravitational Acceleration on Earth 

MSDS Material Safety Data Sheet 

MTBF Mean Time Between Failures 

NASA National Aeronautics and Space Administration 

NDE Nondestructive Evaluation 

NESB Nondestructive Evaluation Science Branch 

NESC NASA Engineering and Safety Center 

NRB NESC Review Board 

OB Need acronym (from Team List) 

OCE Office of the Chief Engineer 

RF Radio Frequency 

RSU Remote Sensor Unit 

RTC Real Time Clock 

RTV Room Temperature Vulcanizing 

SBIR Small Business Innovations 

S/N Serial Number 

SD Secure Data 

SDTO Station Development Test Objective 

SSC Station Support Computer 

SSP Space Shuttle Program 

SSPCB Space Station Program Control Board 

STS Space Transportation System 

TIA Tailoring Interpretation Agreement 

UBNT Ultrasonic Background Noise Test 

US United States 

USB Universal Serial Bus 

V Volt 

VCB Vehicle Control Board 

VOC Volatile Organic Compounds 

VUA VOC Usage Agreement 

WPA Water Processing Assembly 
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00629

Version:

1.0 

Title: 

Development and Certification of Ultrasonic Background Noise 

Test (UBNT) System for use on the International Space Station 

(ISS)

Page #:

43 of 45

NESC Request No.: TI-10-00629 

WLEIDS Wing Leading Edge Impact Detection System 

WSTF White Sands Test Facility 

XML Extensible Markup Language 

14.0 References 

1. Madaras, Eric I, and Prosser, William, “Distributed Impact Detector System (DIDS) Health 

Monitoring System Evaluation”, NESC Technical Report No. 07-035-I, January 14, 2010. 

2. SBIR Phase II contract no. NNL06AA13C, “Distributed Impact Detection System 

(DIDS)”, Contracting Officer Sharon Harper, 2006. 

3. Wilson, William C., Coffey, Neil C., and Madaras, Eric I, “Leak Detection and Location 

Technology Assessment for Aerospace Applications,” TM-2008-215347, September 2008. 

4. SAMS II accelerometer data, 

http://pims.grc.nasa.gov/plots/batch/year2010/month03/day22. 

5. Garcia, Hector, “RTV 142 Offgas Products Memorandum”, Memorandum Number 

TOX-HG-2010-15, July 27, 2010. 

6. Young, Kevin, “Volatile Organic Compound Usage Agreement”, No. 008, 

December 3, 2010. 

7. Ramanathan, R., Ph.D., “Toxicology Assessment for Energizer Iron Memorandum”, 

Memorandum No. JSCTox-RR-04-611.5. 

8. Tran, Dan, “Certification Test Report: Electromagnetic Interference (EMI) for the 

Ultrasonic Background Noise Test (UBNT),” JSC Report no EV5-10-EMC-018R, 

September 15, 2010. 

9. Nguyen, James, “JSC Radio Frequency Authorization”, JSC2010-24, RFA No. 1412, July 

20, 2010. 

10. Koch, Jody, “ISS Electromagnetic Effects Panel Tailoring/Interpretation Agreement”, 

Agreement No. 1160, October 13, 2010. 

11. Barnes, B. G., “Thermal Analysis of Ultrasonic Background Noise Tests Components 

Memorandum”, No. ESCG-4470-10-TEAN-DOC-0177, October 7, 2010. 

12. “JSC Materials and Fracture Control Certification,” Doc. No. MATL-11-008, December 2, 

2010. 

13. Allums, Kimberly K., “Radiation Test Report Invocon Sensor and Micro-SD Cards”, 

Doc. No. ESCG-4430-10-EES-DOC-0023, October 15, 2010. 

14. Jaramillo, Nelson H., “Station Development Test Objective Safety Data package for the 

Ultrasonic Background Noise Test (UBNT)”, ESCG-6110-10-SS-DOC-0789, JSC No. 

65907, December 2, 2010. 

15. “Flight Safety Certificate”, ATV2/NASA/1/081, October 10, 2010. 

16. Nop, J., “Strength, Fracture, and Venting Assessment of Ultrasonic Background Noise 

Tests (UBNT) Assembly Kit Memorandum”, ESCG-4450-10-STAN-DOC-0116, October 

7, 2010. 
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00629

Version:

1.0 

Title: 

Development and Certification of Ultrasonic Background Noise 

Test (UBNT) System for use on the International Space Station 

(ISS)

Page #:

44 of 45

NESC Request No.: TI-10-00629 

17. “Offgas Test Report Request”, WSTF Test Facility No. 10-44571, JSC Request 

No. 13341, August 23, 2010. 

18. Scully, Robert, “Certification of Similarity for Use of an Upgraded Micro-SD Memory 

Card in Hardware Supporting Ultrasonic background Noise Tests (UBNT) Memorandum”, 

October 8, 2010. 

19. Drennan, Jill, “RITF Screening Test Report,” Report no. 100982, TPS No. KY1020007, 

September 8, 2010. 

20. “Derating Analysis of Circuit Protection Devices of Ultrasonic Background Noise Test 

Memorandum”, ESCG Memo No. ESCG-4430-10-EES-MEMO-0026, December 3, 2010. 

21. Jeevarajan, Judith, “EP5 Battery Design Evaluation Form”, EP Tracking No. EP-10-13, 

October 8, 2010. 

22. Energizer Lithium L91 Application, http://data.energizer.com/SearchResult.aspx, Manual, 

Lithium Cylindrical Application Manual

23. L91 Energizer MSDS Document, http://data.energizer.com/SearchResult.aspx, Lithium 

Iron Disulfide Product Safety Datasheet (PSDS)

24. RTV142 MSDS Document, 

http://www.momentive.com/MSDS/showOptions.jsp?Product=RTV142

25. Harper, Susana, “Materials test Data Transmittal” 

Volume II. Appendices 

Appendix A. SDTO Flight Software Manual 
NASA Engineering and Safety Center 

Technical Assessment Report 

Document #:

NESC-RP10-00629

Version:

1.0 

Title: 

Development and Certification of Ultrasonic Background Noise 

Test (UBNT) System for use on the International Space Station 

(ISS)

Page #:

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NESC Request No.: TI-10-00629 

Appendix A. SDTO Flight Software Manual 

This information was not publicly available at time of publication. 
REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

2. REPORT TYPE 

Technical Memorandum

 4. TITLE AND SUBTITLE

Development and Certification of Ultrasonic Background Noise Test 

(UBNT) System for use on the International Space Station (ISS)

5a. CONTRACT NUMBER

 6. AUTHOR(S)

Prosser, William H.; Madaras, Eric I.

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

NASA Langley Research Center

Hampton, VA 23681-2199

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

National Aeronautics and Space Administration

Washington, DC 20546-0001

 8. PERFORMING ORGANIZATION

 REPORT NUMBER

L-20032 NESC-RP-10-00629

10. SPONSOR/MONITOR'S ACRONYM(S)

NASA

13. SUPPLEMENTARY NOTES

12. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified - Unlimited

Subject Category 16 - Space Transportation and Safety

Availability: NASA CASI (443) 757-5802

19a. NAME OF RESPONSIBLE PERSON

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

14. ABSTRACT

As a next step in the development and implementation of an on-board leak detection and localization system on the 

International Space Station (ISS), there is a documented need to obtain measurements of the ultrasonic background noise 

levels that exist within the ISS. This need is documented in the ISS Integrated Risk Management System (IRMA), Watch Item 

#4669. To address this, scientists and engineers from the Langley Research Center (LaRC) and the Johnson Space Center 

(JSC), proposed to the NASA Engineering and Safety Center (NESC) and the ISS Vehicle Office a joint assessment to 

develop a flight package as a Station Development Test Objective (SDTO) that would perform ultrasonic background noise 

measurements within the United States (US) controlled ISS structure. This document contains the results of the assessment.

15. SUBJECT TERMS

International Space Station; on-board leak detection; NASA Engineering and Safety Center; Station Development Test 

Objective; Wing Leading Edge Impact Detection System; Remote Sensor Unit

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3. DATES COVERED (From - To)

March 2010 - April 2011

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869021.05.07.03.13

11. SPONSOR/MONITOR'S REPORT

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NASA/TM-2011-217151

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