Peter M. Struk and Richard C. Oeftering

Glenn Research Center, Cleveland, Ohio

Approach to In Situ Component Level Electronics 

Assembly Repair (CLEAR) for Constellation

NASA/TM—2010-216784

September 2010

AIAA–2009–6472
NASA STI Program . . . in Profi le

Since its founding, NASA has been dedicated to the 

advancement of aeronautics and space science. The 

NASA Scientifi c and Technical Information (STI) 

program plays a key part in helping NASA maintain 

this important role.

The NASA STI Program operates under the auspices 

of the Agency Chief Information Offi cer. It collects, 

organizes, provides for archiving, and disseminates 

NASA’s STI. The NASA STI program provides access 

to the NASA Aeronautics and Space Database and 

its public interface, the NASA Technical Reports 

Server, thus providing one of the largest collections 

of aeronautical and space science STI in the world. 

Results are published in both non-NASA channels 

and by NASA in the NASA STI Report Series, which 

includes the following report types:

• TECHNICAL PUBLICATION. Reports of 

completed research or a major signifi cant phase 

of research that present the results of NASA 

programs and include extensive data or theoretical 

analysis. Includes compilations of signifi cant 

scientifi c and technical data and information 

deemed to be of continuing reference value. 

NASA counterpart of peer-reviewed formal 

professional papers but has less stringent 

limitations on manuscript length and extent of 

graphic presentations.

• TECHNICAL MEMORANDUM. Scientifi c 

and technical fi ndings that are preliminary or 

of specialized interest, e.g., quick release 

reports, working papers, and bibliographies that 

contain minimal annotation. Does not contain 

extensive analysis.

• CONTRACTOR REPORT. Scientifi c and 

technical fi ndings by NASA-sponsored 

contractors and grantees.

• CONFERENCE PUBLICATION. Collected 

papers from scientifi c and technical 

conferences, symposia, seminars, or other 

meetings sponsored or cosponsored by NASA.

• SPECIAL PUBLICATION. Scientifi c, 

technical, or historical information from 

NASA programs, projects, and missions, often 

concerned with subjects having substantial 

public interest.

• TECHNICAL TRANSLATION. Englishlanguage translations of foreign scientifi c and 

technical material pertinent to NASA’s mission.

Specialized services also include creating custom 

thesauri, building customized databases, organizing 

and publishing research results.

For more information about the NASA STI 

program, see the following:

• Access the NASA STI program home page at 

http://www.sti.nasa.gov

• E-mail your question via the Internet to help@

sti.nasa.gov

• Fax your question to the NASA STI Help Desk 

at 443–757–5803

• Telephone the NASA STI Help Desk at

 443–757–5802

• Write to:

 NASA Center for AeroSpace Information (CASI)

 7115 Standard Drive

 Hanover, MD 21076–1320
Peter M. Struk and Richard C. Oeftering

Glenn Research Center, Cleveland, Ohio

Approach to In Situ Component Level Electronics 

Assembly Repair (CLEAR) for Constellation

NASA/TM—2010-216784

September 2010

AIAA–2009–6472

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135

Prepared for the

Space 2009 Conference and Exposition

sponsored by the American Institute of Aeronautics and Astronautics

Pasadena, California, September 14–17, 2009
Acknowledgments

The authors wish to acknowledge the following individuals for their contribution to this work: Eric. E. Anderson, Martin A. 

Bradish, John W. Easton, Gregory P. Funk, Gary E. Gorecki, Alain Izadnegahdar, Jeffery R. Juergens, Michael J. Lewis, Duc K. 

Truong, Daniel R. Vrnak, and Raymond P. Wade. The authors acknowledge the contribution of various other NASA organizations 

including the Logistics and Maintenance group at Johnson Space Center, the NASA Spacecraft Services Depot and NASA Shuttle 

Logistics Depot. Also, This work was funded by the Supportability Project in NASA’s Exploration Technology Development 

Program Offi ce (Mr. Barmac Taleghani, Program Manager, NASA Langley Research Center). 

Available from

NASA Center for Aerospace Information

7115 Standard Drive

Hanover, MD 21076–1320

National Technical Information Service

5301 Shawnee Road

Alexandria, VA 22312

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

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

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

either expressed or implied, by the National Aeronautics and 

Space Administration.

Level of Review: This material has been technically reviewed by technical management. 
NASA/TM—2010-216784 1

Approach to In Situ Component Level Electronics 

Assembly Repair (CLEAR) for Constellation

Peter M. Struk and Richard C. Oeftering

National Aeronautics and Space Administration

Glenn Research Center

Cleveland, Ohio 44135

Abstract

NASA’s Constellation Program for exploration of the Moon and Mars places human crews in 

extreme isolation and resource scarce environments. Maintenance resupply is a significant issue for such 

long duration missions. Currently, the International Space Station (ISS) approaches maintenance 

primarily around replaceable modules called Orbital Replacement Units (ORU). The process of swapping 

out ORUs has served the ISS well and kept crew time for maintenance to a minimum. However, this 

approach assumes a substantial logistics capacity to provide replacement ORUs and return ORUs to Earth 

for repair and return to service. The elimination of the Space Shuttle substantially reduces the supply of 

replacement units and virtually eliminates the return for repairs.

The modular ORUs used for ISS require relatively large blocks of replacement hardware even though 

the actual failed component may really be several orders of magnitude smaller. Electronic ORUs are 

typically modular assemblies that may include several internal circuit cards. While being able to access 

and replace smaller sub-assemblies such as circuit cards is critical, a capability to repair failed electronic 

hardware at the component level offers the most potential for reduced resupply mass. Furthermore, such 

repair capabilities help to enable the crew to better respond to unforeseen faults and achieve more 

resource independence which becomes significantly more important as humans venture further away from 

Earth. A capability to repair at the component-level within the confines of a spacecraft requires significant 

planning and investment by NASA beginning early in the design phases of a mission.

The Component Level Electronics Assembly Repair (CLEAR) task was created to explore electronics 

repair for future manned space missions. From 2006 to 2009, CLEAR was managed under the 

Supportability project of the Exploration Technology Development Program. This paper describes the 

activities and accomplishments of CLEAR. These include making a case for component-level electronics 

repair, examination of current terrestrial repair hardware and potential repair needs. Based on those needs, 

the CLEAR team proposes an architecture for an in-site repair capability aboard a spacecraft or habitat.

The repair architecture, which includes a combination of manual and semi-automated tools, would allow 

the crew to diagnose, repair, and test electronics down to the component level while minimizing spares 

payload with minimal crew time and training. Additionally, this paper discusses recent progress toward 

developing in-space repair capabilities—including two spaceflight experiments—and presents technology 

concepts which could help enable or benefit the same.

1.0 Introduction

NASA’s plans for long duration missions to the Moon and, especially, to Mars require a much greater 

degree of self sufficiency on the part of the crew than ever before. Such missions will have greatly 

reduced logistic support from Earth compared to International Space Station (ISS). Returning to Earth in 

the event of an emergency may not be an option either, as a lunar return flight could require two to three

days, and a Martian return flight will require much longer. 

One area of mission support that NASA must plan for is electronic repairs. Although more reliable 

than predicted, electronic systems aboard the Space Shuttle and ISS have experienced faults leading to the 

use of backup systems or loss of capability to some degree (Refs. 1 and 2).Therefore, it is likely that 

crews of long duration space missions will likely encounter an electronics failure at some point during a 
NASA/TM—2010-216784 2

mission. With the design of the Crew Exploration Vehicle (CEV) already well underway and likely 

influencing the design of future spacecraft and hardware, it is important for NASA to begin examining

and designing techniques and tools for crew members to conduct electronics repair during long duration 

space mission. These considerations include system design (for accessibility, parts type and sizes, and 

board complexity), repair infrastructure (including diagnostic capabilities, tools, and other needed 

equipment), and logistics constraints. The decisions on how to approach each of these considerations 

depends on the overall repair strategy chosen.

The historical approach to electronics repair on manned spaceflight missions, particularly those 

aboard ISS, has been to replace modular subassemblies called Orbital Replacement Units (ORU’s). The 

astronauts simply replace the malfunctioning ORU with a spare and then return the faulty ORU to Earth

via the Space Shuttle. This approach allows for simplicity in the diagnosis of the problem, as the fault 

only has to be isolated to a given ORU, rather than determining the fault down to the component level.

Crew training and experience in performing repairs are minimized. Once on Earth, the faulty ORU is 

diagnosed, repaired, and then returned to a pool of spares awaiting re-use in space. With this approach, 

there is a high degree of confidence in the repair, as the ORU can be tested extensively on the ground 

prior to being relaunched to the ISS.

Conversely, this approach carries with it a severe penalty in terms of the logistics support required

(and overall cost to the program). Conceptually, it is easy to imagine the penalty in mass and volume that 

is levied when an entire ORU is launched to remedy a failure of a single, small component such as a

resistor, transistor, or other electrical component. While this approach is expensive, it may be acceptable 

for low Earth orbit (LEO) missions if resupply arrives on a regular basis (large quantities of spares are not 

easily stored in orbit). The resupply interval for the ISS can be as short as a month although early mission 

planners expected more frequent intervals. For future missions beyond low Earth orbit, the interval 

between resupply is anticipated to be significantly greater. For example, the resupply interval for the 

planned lunar outpost is just greater than six months.

Alternatives to the ORU replacements are lower-level repairs. Such repairs can include replacement 

of lower-level units (also called shop-replaceable units or SRUs), for example circuit board-level swapouts. A further level of repair could then be repairing the board itself at the component-level. This could 

serve to greatly reduce the planned-spare ORU requirements, while providing a capability to handle 

unforeseen repair contingencies. The need to handle such unexpected events has been illustrated by 

several events in NASA flight history. The successful conclusion of the Apollo 13 mission, after an 

explosion severely damaged the service module, highlights the benefits of having the capability to 

implement on-the-spot repairs. The consequence of failing to allow for off-nominal repairs can be 

inferred from the loss of the shuttle Columbia; even if the crew had been aware of the problems with the 

leading edge tiles, they were not equipped to make repairs in-flight. Since that incident, NASA has made 

considerable efforts to allow for contingency repairs of problems of that nature (Ref. 3).

As part of the NASA Supportability project of the Exploration Technology Development Program, 

the Component-Level Electronics-Assembly Repair (CLEAR) task was established to examine, and to the 

extent possible, demonstrate the feasibility of how crew-members could effectively perform electronic 

repair down to the component level. In this document, the acronym CLEAR is used to refer both to the 

task (e.g., project team name) as well as the process of component-level electronics assembly repair. The 

objectives of CLEAR are composed of four primary areas which are the basic elements of the repair 

process:

1. Diagnose electronics assemblies to identify faulty component(s) with equipment that fits within 

the mass, volume, and power constraints of spacecraft.

2. Repair electronics down to the component-level in-situ with processes and materials that are safe 

and compatible with the space environment which allows the crew to make the necessary repair.

3. Evaluate (e.g., test) and determine that the repaired circuit is safe to return to service.

4. Augment the flight crew with knowledge and skills to diagnose faults and perform repairs without 

expanding crew size.
NASA/TM—2010-216784 3

These areas are investigated by a combination of trade studies, analysis, ground based testing, 

reduced gravity aircraft testing, and actual spaceflight testing aboard the ISS in two experiments. This 

paper summarizes activities under CLEAR from 2006 to 2009 which include several other papers (Refs. 4

to 7) available in the public domain as well as other unpublished reports which receive more emphasis 

here. Specifically, this paper presents a case for lower-level electronics repair, describes what sort of 

repairs might be necessary, and provides a conceptual architecture to meet those needs. The architecture 

is intended for use as part of a future lunar or Martian base but is applicable to the ISS or other space 

vehicles or habitats intended for long-duration use.

2.0 The Case for Electronics Repair

2.1 Examining the ISS

For insight into actual space repair needs, an internal study examined the operational experience of 

the ISS program through the Problem Reporting and Corrective Action (PRACA) database specifically 

for electrical and electronic system problems. The ISS has higher than predicted reliability yet, as 

expected, it has persistent problems. A goal of this study was to identify which on-orbit electrical 

problems could be resolved by having a robust component-level repair capability available (such as that 

described later in this paper). A further goal was to identify problems that could benefit from the 

additional diagnostic and test capability that complement a component-level repair capability.

The study indicated that many problems stem from a small set of root causes that also represent 

distinct component problems. A subset of these recurring problems, listed as “root cause unknown,”

remained unresolved due to limitations in current telemetry, built-in test capability, and available 

diagnostics. The study concluded that roughly 42 percent of on-orbit electrical problems on ISS could be 

addressed with a component-level repair. Furthermore, 63 percent of on-orbit electrical problems on ISS 

could benefit from additional external diagnostic and test capability. Problems that would not benefit 

from a component-level repair capability stem from software, operations, or documentation errors as well 

as single-event upset (SEU) errors which can be cleared by a register refresh or by executing an error 

correction code. If no permanent damage occurs, then a component repair is not needed. Additionally, 

lighting problem which require replacement bulbs (i.e. a logistics end-of-life issue) were not considered 

repairable. Overall, these results indicate that in-situ component-level repair in combination with 

diagnostic and test capability can be expected to increase system availability and reduce logistics. 

2.2 Life-Cycle Cost and Resupply Mass Impacts of Lower-Level Electronic Repair

An internal project study examined the impacts to life-cycle cost and resupply mass on maintaining 

electronic hardware by comparing different approaches for in-situ repair of electronic hardware. The first 

approach, which was the baseline to compare against, was replacement of ORUs as is currently performed 

on the ISS. The second is replacement of SRUs or board level swap outs. Currently, the ISS has one ORU 

—the Multiplexer Demultiplex (MDM)—which allows for in-situ board-level swap out. The third repair 

strategy was component-level replacement at the board level. The third strategy is similar to the SRU 

replacement in that SRUs need to be removed from the system. Instead of being discarded as in option 2, 

the crew repairs the SRUs which are returned to service or designated as functional spares. For both 

options 2 and 3, it was assumed that the ORUs are designed to allow access to the lower board levels.

This study generated a life-cycle cost model using existing data from ISS Criticality (Crit) 1 hardware 

(which denotes life or mission critical items) to investigate the impact on life-cycle cost for different 

repair strategies. The resulting subset of hardware consisted of sixty-seven different types of electronic 

ORUs representing many ISS support systems whose functions are expected to be represented in the 

Lunar Outpost such as power, communications, life support, and command and data handling. The data 

used came from two primary data sources: the ISS Modeling Analysis Data Set and the ISS Logistics 

Access data file prepared by Robert Shisko from the NASA Jet Propulsion Laboratory. This study was 

limited to historical data of Crit 1 hardware (highest reliability) due to the availability of data at the SRU 
NASA/TM—2010-216784 4

level for Crit 1 systems. Crit 2 and lower systems do not have the SRU data readily available and would 

take considerable time to generate for each system. Furthermore, Crit 1 hardware was selected to 

minimize the crew labor for performing SRU or component level repairs. Some SRUs are common 

between ORUs allowing spares to consist of a percentage of the operational ORUs (which can be 

swapped from location to location). Mean Time Between Failure (MTBF) numbers were used to generate 

expected failures and are the current ISS values that have been updated throughout its lifetime.

For the component-level repair option, a conceptual repair and diagnostic station was developed for use in 

this study similar to that proposed later in this paper. This system involves a combined semi-automated 

diagnostic and rework station, supplemented by a manual repair capability which significantly surpasses 

the current capability on ISS. The system also involves telemetry with ground support personnel so as to 

assist the crew in performing the diagnostics and repair functions. This study assumes that the technology 

needed for such a capability is at a Technology Readiness Level (TRL)–6, as defined by NASA (Ref. 8).

The development effort to go to TRL 9 is accounted for in this analysis assuming that the technology 

starts at TRL 6.

The life-cycle cost model shows that ORU-level repair of the ISS hardware used for this study over a 

10 yr, steady-state, operational period had a total cost impact of $818M. This includes the initial cost of 

the ORU, spares, launch, and maintenance. By implementing a capability to conduct SRU level 

replacement, the initial investment and operating cost was reduced to $149M (an 82 percent savings).

By implementing SRU and component level repair strategies, these costs were further reduced to $130M 

(an 84 percent savings). All alternatives included the development costs of unique flight support 

equipment required for maintenance. The model also captured crew time impacts including both EVA 

and IVA activities over a 10-yr period. Relative to ORU replacement (1833 hr), crew time increased by 

28 percent (2340 hr) with SRU-level replacement while component-level repair of the SRUs increased 

crew time by 51 percent (2767 hr). Note that the EVA time (420 hr) does not change between alternatives 

because the numbers of external ORUs failures do not change (only the maintenance approach).

An ORU case study was used to determine the impact to mass for board-level and component-level 

sparing. Based on this information, a conceptual ORU was generated which had twelve operational units 

(29.16 kg). This ORU was performing a strictly electrical function (power switch). To maintain an 

operational status, the MTBF data for the ORU indicated two spares would be required for a 180 day 

resupply interval (4.86 kg). Implementing a board level replacement would require two spare cards 

(0.86 kg, or an 82 percent reduction in spares mass). Using the MTBF data for the components used 

within the system, a spare component kit (0.20 kg, or a 96 percent reduction in spares mass) could be used 

to maintain operational status. These results are consistent with the life-cycle cost model which showed a 

95 percent reduction in spares mass system wide for the component-repair option. Thus, the component 

repair option offers the lowest potential sparing mass.

In summary, component level repair offers both cost benefits and mass savings for extended space 

missions. The results show that once you deviate from ORU replacement to lower-level SRU 

replacement, component-level repair does not add additional cost but rather saves costs over the life-cycle

even when including the development cost of the added flight hardware. The cost and mass saving would 

be expected to further increase with the inclusion of lower criticality but still important hardware (like 

science payloads which are critical to the success of a mission). During future missions, the ability to 

perform repair of electronic systems will be required and repairs below the ORU level offer mission 

flexibility and enhanced safety with a capability to respond to unanticipated failures of electronic 

hardware. This includes risk mitigation from design errors and common mode faults due to an increased 

commonality amongst hardware. Furthermore, the inability to bring back faulty hardware due to severe 

return mass limitations necessitate the need for in-situ diagnostics to understand why systems have failed.

Additionally, the ability to perform component-level repairs improves the ability to operate within 

maintenance resource limits. Such a repair capability comes at the expense of increased crew time 

needed. This increase can be minimized by incorporating tele-operations, automation, and a supportability 

strategy which considers component-level repair during the mission design phase.
NASA/TM—2010-216784 5

3.0 Establishing the Capabilities Needed for Electronics Repair

3.1 Current Terrestrial Repair Capabilities

To determine the capabilities needed studies examined current technology, current repair practices 

and how repairs of flight systems are organized. The following are the three primary aspects of a 

complete repair process.

3.1.1 Diagnostic Activities

Diagnosis involves examination, observing symptoms, and measuring fundamental parameters to, 

first, characterize the fault, and second, determine the root cause of a malfunction or fault. It may involve 

a passive circuit in a power-off condition or an active circuit in a power-on condition. Furthermore, there 

may be a series of probing measurements intended to locate a problem area followed by refined probing 

to isolate the problem. For diagnostic operations, the emphasis is on measurements that help isolate a 

specific cause among many possible causes.

3.1.2 Repair Activities

Repair is broadly defined as a physical replacement, rework, or remanufacture of a faulty or failed 

circuit element and restoring full function. Most often it involves replacement of faulty components or the 

rework of interconnecting hardware such as solder joints, connectors, or the underlying substrate. In most 

cases, a failed component is replaced. It is rare that the component itself is amenable to repair (e.g., 

transformers). Thus for clarity, repair activities actually are replacement of parts at the component level.

3.1.3 Functional Test Activities

Functional test is intended to verify that a circuit functions properly in accordance with functional 

requirements for that system. Direct electrical measurements are made to determine if the unit is meeting 

its design specifications. Verifying function implies operating (or simulating operation) and observing the 

circuit as it performs its function in its operational environment. Functional testing often follows the 

assembly sequence where functional tests are performed at the lowest to the highest levels of assembly.

Functional tests include built-in tests (BITs) for both software and hardware, physical parameter 

measurement, and recording observed behavior in nominal and off-nominal operations. Ultimately, a 

circuit must be tested as part of the actual system (or simulated system). Early during the project, the 

CLEAR team conducted a survey examining the tools and devices used to conduct component-level 

diagnostics, test, and repair in terrestrial settings. Diagnostic devices include instruments to measure 

characteristics of the component or circuit including voltage and resistance measurement, oscilloscopes, 

and a variety of signal generators and network analyzers. Other key diagnostic devices include power-off 

testers which apply low voltage signals to a component or node and compare the result to a known good 

sample. Such information can help determine the location of a fault on a circuit board. Additionally, the 

survey examined functional testers which emulate external systems at the inputs and outputs of a circuit 

board to verify proper operation and to isolate faults. Key components of functional test systems are 

shown in Figure 1.

The tools used for performing the physical repair include a variety of hand and soldering tools, 

including common resistive soldering irons, hot air devices, infrared soldering, and laser soldering 

systems. Many of the tools are discussed elsewhere in this paper. The survey also examined semiautomated rework stations. Finally, the study surveyed the types and methods to remove conformal 

coatings which protect a circuit board. Data was tabulated for mass and volume of existing tools, 

capabilities, and disadvantages of the tools in a space environment.
NASA/TM—2010-216784 6

Figure 1.—Conventional functional test systems involve interface emulators, data loggers, signal 

monitors, signal stimulus sources, measurement instruments, power supplies, and load simulators 

(with cooling).

3.2 Current ISS Repair Capabilities

Current electronics repair strategies on the ISS focus on removing an ORU with faulty electronics and 

replacing it with a spare unit. With the exception of the MDM discussed previously, current ORUs have 

not been designed to readily remove circuit cards from higher-level assemblies. Using built-in test (BIT) 

capabilities and an external test kit, the crew can isolate a fault on an MDM to the circuit card level. The 

crew then uses a circuit card puller to remove the faulty circuit card. Such a design strategy helps 

facilitate circuit card removal and is recommended for future designs employing circuit cards. However, 

the crew does not attempt a component-level repair at the circuit card level.

The ISS crew also has access to some tools suitable for electronics repairs. The crew has access to 

two soldering irons including one provided by the Russians as well as the United States (U.S.). The 

Russian iron is a capillary flow type soldering iron which is powered by a constant voltage power source.

However, further information on the Russian iron is limited. The U.S. Soldering Kit has a battery 

powered soldering iron, two Weller PT Series 600 °F soldering iron tips, a spool of solder wire, solder 

wick, and heat sinks for performing limited soldering and desoldering tasks. This kit has been used in the 

past for some repairs (Ref. 9), scientific research (Ref. 10), as well as engineering studies on solder joint 

formation (Refs. 11 and 12) and manual component-level repair (Ref. 12). These engineering studies were 

conducted by the CLEAR team and are discussed more in Section 5.0. While useful, this soldering kit is 

not ideal for repairs of circuit cards at the component level. Some shortcomings include the maximum tip 

temperature and temperature control methods as well as the limited number of solder tips available.

Section 5.4 discusses recommendations to improve soldering capabilities for future space missions.
NASA/TM—2010-216784 7

Figure 2.—Astronaut Sunita Williams conducts a 

soldering experiment within the Maintenance 

Work Area aboard the ISS.

The crew members conduct soldering tasks within a 

containment system, a tent-like glovebox with clear plastic 

sides mounted on the Maintenance Work Area (MWA).

Figure 2 shows astronaut Sunita Williams using the MWA 

with the containment system for soldering aboard the ISS.

The containment enclosure traps debris to help prevents 

contamination of the cabin or life support equipment. The 

containment system has a small Fresnel lens window that 

provides a small amount of magnification within the work 

area. The containment system also includes two 

feedthroughs, one for a vacuum hose to collect gases and 

debris evolved from the soldering process, and another to 

provide power to instruments, such as video cameras, 

within the work area. The containment system, while 

effective at containing debris formed during soldering, 

does have some limitations. The containment system is 

designed to collapse and fold for storage; performing this 

operation multiple times has created many creases and 

folds in the system walls, making it difficult to see through 

any area but the Fresnel lens. The containment system is 

also somewhat tall, leading to a large distance (on the 

order of 12 in.) between the work piece and the crew 

member’s eye. This can make seeing the work piece 

difficult with the naked eye, and limits the effectiveness of 

a magnifying lens visor provided for the crew because the 

work piece is beyond the focal length of the lens. This 

distance between the work piece and closest viewing 

location can also have ergonomic effects, and become 

uncomfortable for tall crew members. Finally, the MWA and containment tent take 30 min or more to 

setup up which has a significant impact on crew time.

Crew members also have access to a wide variety of additional tools as shown in Figure 3. For 

example, the ISS Pin Kit contains jumper wires with various terminations, connectors, pin, and lugs for 

making wire connections. The various drawers of the Inner Vehicular Activity (IVA) Tool Kit contains a 

number of common hand tools, most of which are appropriate for mechanical rather than electronics 

tasks, but does include crimper tools used with the pins and lugs found in the Pin Kit. The recent 

Component Repair Experiment (Ref. 12) aboard ISS included a small tool kit augmenting the tools 

already on orbit. The additional tools included standard and fine tip cutters; three types of tweezers, a 

dental pick for scraping conformal coating or manipulating small component legs; soldering iron tips 

appropriate for smaller components; a fiberglass stick for rubbing conformal coating off the circuit board; 

and liquid flux, flux cored solder wire, and solder wick. These tools remain aboard the ISS and are 

available for future use. Finally, the crew also has access to some limited diagnostic and testing devices 

including a combination multimeter and oscilloscope, logic analyzer, power supply, and other basic 

electronics diagnosis tools, as well as the dedicated MDM tester already discussed.

Repair tasks aboard the ISS depend on extensive guidance from ground support teams. These teams 

collect data and reports from the crew after a failure, and use this information in an attempt to determine 

the cause of the fault and a potential solution to the failure. These efforts range from working on fully 

functional mock-ups of flight instruments and systems on the ground, to communicating and meeting with 

the developer of the hardware, whether within NASA or an outside vendor. The team then develops and 

test procedures for a repair, a process that often requires intensive work. The procedures are then 

transmitted to the crew who, guided by the procedures, attempt to perform a repair and return a faulty 

system or device to a functional state.
NASA/TM—2010-216784 8

Figure 3.—A sample of tools available aboard the ISS.

3.3 In-Situ Repair Needs for Electronic Systems of Future Spacecraft

It is likely that the first operational need for component-level repair capabilities is during longduration outpost stays on the Moon and especially Mars. However, the ISS is a prime location to evaluate 

such technology and, because of the retirement of the space-shuttle in 2010, may benefit from a repair 

capability to help sustain systems with reduced logistical support. To better understand what types of 

electronic components would need to be repaired, the CLEAR team investigated electronic systems to 

determine the nature of the circuits used during spaceflight. The information was used as a basis to 

develop an architecture that addresses electronic diagnostics, repair, and testing needs, and the practical 

constraints of operating in a space environment.

As circuit repair is very dependent on the manufacturing processes, this study relied on data gathered 

from the ISS Vehicle Master Database (VMDB) for relevant information on design, development, 

fabrication, and test practices. The rationale for using the ISS is based on the current state of the 

Constellation Program (CxP) designs and the fact that the ISS is the only predecessor for electronics 

composed of modular orbital replaceable units (ORUs)—design practices used for CxP will likely be 

derived from ISS experience. New CxP spacecraft such as the Orion are expected to employ state of the 

art field programmable devices and high density grid array packaging. Because lunar outpost is over a 

decade away, advances in electronics at the component level will affect diagnostics, repair, and test 

technology. The electronics industry however, has shown signs of maturing and the rate of performance 

increase is slowing. Therefore, electronic equipment designed for the current generation spacecraft are 

expected to be relevant for lunar applications. 

Finally, the study also made some unexpected but important findings regarding information access 

and the ability to formulate diagnostic, repair, and test solutions for electronic circuits. It was found that 

too much of the information provided in the ISS VMDB is subject to the discretion of the original vendor. 

Pin Kit

IVA Tool Kit (5 drawers)

t

Power Drill

Ethernet Repair 

Crimp Tool

t

Current 

Probe

Power Supply

1553 Databus 

Analyzer

Logic Analyzer

Breakout Box
NASA/TM—2010-216784 9

The viability of component-level repair depends heavily on rapid access to detailed design information, 

including the process and materials used in a circuit’s construction. Such information accessibility must 

be built into CxP.

3.3.1 Diagnostics and Functional Test

Terrestrially, repairs typically require dedicated equipment to perform initial diagnostics and post 

repair functional tests. Conventional diagnostics and test equipment for a single unit may require multiple 

racks, while repair equipment could fit in a single drawer. Constellation needs a suitably scaled solution 

to diagnostic and test equipment. An attempt to provide an all-in-one solution that can address the wide 

array of all electronics boards and their diagnostic needs would most likely result in a prohibitively heavy 

and difficult system. The approach proposed herein concentrates on those capabilities that would best 

address the greatest number of common diagnosis and repair situations, without attempting to provide a 

capability that will work in all situations. Understanding the types of signals indicates the type and 

quantity of equipment needed. For diagnostics and functional testing, channel count, frequency 

bandwidth, and dynamic range are important parameters. Figure 4 and Figure 5 indicate the electrical 

signal needs based on the typical elements of the ISS. 

Figure 4 shows the bandwidth, channel count, and dynamic range for several ISS ORUs. Although 

the MDM (Figure 4) is distinct in that it has a large dynamic range and high channel count (480 I/O 

signals), it is not necessary to perform simultaneous testing of all 480 channels. By testing SRU-level 

circuit cards, the highest channel count can be reduced to 128 channels. By further limiting tests to a 

particular channel type, the channel count can be reduced to 32. This illustrates that diagnostics below the 

ORU level can be much simpler and help minimize the demand for large test sets. Further, SRU level 

diagnostics isolates the faulty component. 

Figure 4.—ISS Analog Signal Gamut.
NASA/TM—2010-216784 10

As expected, RF communication is most demanding, in terms of bandwidth and dynamic range. A 

down converter can be installed between the RF electronics and the diagnostics and test equipment that 

operates at an analog baseband frequency. By the nature of analog device technology, it is difficult to 

build-in self test capability. Thus diagnostics and test of analog electronics will require external 

equipment.

Figure 5 characterizes the digital signals of ISS electronics based on two variables: signal speed and 

channel count. Digital devices and their signal speeds are very subject to change with advances in digital 

technology. For example, the MDM bus is based on early 1990s technology and were already obsolete by 

the time they were deployed. The current generation digital processors have one to two orders of 

magnitude increase in performance. The newest generation of CxP avionics will exploit a high speed 

serial data bus such as 1394B and GigaBit Ethernet will also impact diagnostic instrumentation. Although 

the new architectures have very high data throughput, they also require a much smaller set of signal 

channels which simplifies the physical connection needs.

An important benefit of advances in processor speed and memory capacity is the greater capacity for 

built in diagnostics and test capability. By increasing the capability of embedded or built in diagnostics, 

the need for external equipment is reduced. Embedding these capabilities has little or no impact on weight 

and volume. Since most hardware is controlled by embedded controllers built in diagnostics should be 

widely used.

Figure 5.—ISS Digital Signal Gamut.
NASA/TM—2010-216784 11

3.3.2 Manual Repair Processes

The ease or difficulty of component-level repair depends on multiple factors, including the placement 

of the hardware, the ease of access, the equipment provided, the time and effort required, the basic skill 

set provided by the crew, and the working environment. Aside from diagnostics and test, the repair 

process includes retrieval, work area preparation, the mechanical disassembly of the housing, and 

extraction plus replacement of the faulty circuit, followed by the reassembly and reintegration of the

ORU. At higher ORU and SRU levels, assembly accessibility is a dominant issue. Once a target Circuit 

Card Assemble (CCA) has been removed and can be freely handled by the crew, the repair becomes more 

dependent on the initial manufacturing materials and processes and how well the crew is equipped to 

rework them. In some instances, a hand-soldered assembly should readily be reworked by hand soldering 

techniques; however, circuits involving high density integrated circuits constructed by a solder reflow 

process will require more sophisticated techniques.

For manual soldering, an innate dexterity is important, but a sense of timing and patience is also 

required. Gauging the effectiveness of the iron’s temperature setting and recognizing indications that the 

process is not performing properly is a skill set that only comes with practice and experience. Training 

can expose the crew to the fundamentals, but consistent quality results from experience and practice.

Without the benefit of constant practice, it is unreasonable to expect a crew member to achieve highquality repairs without substantial assistance. When compared to soldering processes used in 

manufacturing that employs programmed machinery, highly tuned processes, and constant process 

monitoring, the act of manual soldering is actually more complex and inconsistent. Manual soldering 

must be limited to applications that are simple and can tolerate some inconsistency.

Manual soldering is effective for simple tasks like soldering a discrete leaded device or attaching a 

wire. Both the limitations of conductive solder techniques and human dexterity contribute to difficulty as 

the thermal conductivity increases and the lead size decreases. For manual conductive solder repair, the 

ability to bring the temperature of the soldered joint up to the melting point quickly with minimal impact 

to the board substrate or device package is critical. Parameters that affect the heat transfer contribute 

directly to the effectiveness of the reliable joints. As the lead pitch becomes finer, it becomes 

progressively harder to solder with a conventional iron. Solder iron tips are sized to match the lead size.

Smaller tips may not be able to keep up with the heat conducted out by a highly conductive substrate.

Preheating is one technique that extends the operating range of the solder iron however, it also adds steps 

and equipment to the process.

Certain repairs are more amenable to manual repair processes without additional fixtures and are 

more effective than an automated process. For example, point-to-point wiring can be difficult to automate 

without extensive fixtures. For plated through-hole (PTH) components, the primary advantage is that 

devices can be positioned and, if needed, crimped so that they essentially self-fixture. Discrete and lowpin-count PTH integrated circuits (ICs) are generally easier than surface mount technology (SMT) for 

manual methods. Surface-mount devices can be simple to solder if the part is prefixtured by an adhesive 

although this becomes a deterrent later if the component is to be removed again. For ICs with high pin 

counts, a self-crimped PTH is much easier to handle manually than free SMT ICs. For soldered high 

density grid array devices like ball grid arrays (BGA) and land grid array (LGA), manual iron methods 

are simply not viable and such devices are exclusively reflow repair operations.

3.3.3 Automated Reflow Processes

Solder reflow has been universally adopted by industry because it can be easily setup and run with 

modest equipment and relatively few steps. Given appropriate preparations, a quality product can be 

produced with equipment that is essentially a sophisticated convection oven. Solder pastes are formulated 

to consistently activate the flux, melt, and wet out components at a predefined temperature. Solder pastes 

are dispensed by automated syringe dispensers or by a silk screening method that applies solder over the 

entire board in one operation. For reflow, CCA package factors that affect process complexity are 

different from those that affect the manual methods. For example, reflow is insensitive to the number of 
NASA/TM—2010-216784 12

leads since all leads are processed simultaneously. Finer lead pitch increases the need for precise 

placement of the device, and metering of paste dispensing becomes more precise.

The primary difference between the reflow process used in manufacturing and the reflow process in 

repair is the need to localize the reflow heating to the target component without disturbing the solder of 

adjoining parts, which is accomplished by preheating the overall circuit board. By preheating the board to 

roughly 100 °C below the melting temperature, the stress on the board is reduced, the heat flux conducted 

away from the target component is reduced, and the time to bring the target component to reflow 

temperature is reduced.

Spacecraft electronic CCAs are often equipped with integrated conductive heat-sink plates, thus a 

preheat process is essential to minimizing the plate’s cooling effect. The large conductive paths may also 

provide a means of preheating a circuit. It is possible to construct a heater that mates to the circuit card in 

the same manner as the chassis mates to the circuit card. In this case, the interface acts as a circuit card 

preheater.

As discussed earlier, CxP should expect future circuits to include grid array packages. Both LGA and 

BGA exploit the relatively large surface on the underside of an IC package. The larger real estate allows 

the design to provide greater lead spacing. Both LGA and BGA packages can tolerate more misalignment 

and void fraction that an equivalent perimeter lead flat pack. LGA can tolerate a full 50 percent 

misalignment and greater than a 25 percent void fraction. All these factors indicate that, for an equivalent 

lead count, grid arrays are easier to rework with an appropriate reflow system than conventional surfacemount devices.

In summary, component-level repair will involve integrated circuit packaging that is expected to 

migrate from perimeter-mounted through-hole and surface-mount technologies to ball grid and land grid 

array technologies. This trend limits manual solder repair methods to conductors, connectors, and simple 

discrete devices. High-density ball grid and land grid array devices must be repaired using automated 

techniques. Examination of circuit assemblies for spacecraft indicates that conductive cooling will be 

used throughout and circuit repair will require preheating.

4.0 Operational Concept and Architecture for In-Situ Electronics Repair

4.1 Merging of Flight and Depot Operations

For CLEAR the operational concept involves substantial human activity on Earth and in space with 

the intent of correcting in flight electronics problems. It encompasses existing organizations and practices 

while incorporating new capabilities aimed at empowering the crew in the repair of in-space electronics.

The operational concept also includes scenarios where stepping through a repair process indentifies 

capabilities needed. The operational concept is ultimately used to define the CLEAR architecture. As 

described previously, the repair process is composed of three primary activities: diagnostic, repair, and 

functional test. Although these activities may employ the same resources and equipment, they have 

distinctly different objectives and, in turn, drive different requirements.

The proposed operational concept for repair combines crew-interaction with tools that will allow both 

manual and semi-automated operations. Generally, it is assumed that the ORU assembly will be broken 

down manually by the crew. This includes manual removal of ORU subassemblies, typically CCAs for 

electronic assemblies, and breaking the mechanical and electrical interconnections. The faulty hardware 

or CCA is brought to a workstation where it is to be diagnosed and/or repaired. To assure high utility this 

workstation could have elements which are removable and portable which may be particularly useful 

when moving an ORU to the workstation is impractical (for example, performing in-situ diagnostics for 

system troubleshooting prior to ORU removal). This workstation is only part of an overall CLEAR System 

Architecture.

The CLEAR System Architecture is intended to support diagnostics, repair (component replacement), 

and functional testing for electronic systems. For semi-automated operations, the goal is to reduce crew 

time usage to the extent possible. Semi-automated operations are conducted by remote control of 
NASA/TM—2010-216784 13

equipment or machinery via telecommunications links and often referred to as tele-operations. The bulk 

of the human activity will be performed by ground-based engineering crews working largely offline.

Depending on the application, the equipment may or may not require crew intervention during operations

but the intent is to offload as much crew workload as possible and to offset the added operations involved 

with component level repair. The supporting crew may be formed from hardware vendors, system 

managers, integrators, and engineering and technical staff of NASA repair depots.

Repair operations are expected to be infrequent; the cost of keeping a “standing army” of teleoperators on standby would defeat the benefits of tele-operations. The CLEAR Operational Concept 

proposes that support teams be built on an as-needed basis similar to current ISS operations. Such a team, 

referred to here as the CLEAR Tele-operations Engineering Support Team or CLEAR TEST would 

provide the following:

• Specific ORU hardware and software knowledge

• Diagnostic and test expertise

• Materials and process expertise

• CLEAR hardware programming, verification, and validation support

• VMDB and CLEAR process library configuration management

• Hardware and spares tracking

• Coordination of flight crew operations

• Coordination of tele-operation and execution of CLEAR diagnostic, repair, and functional test 

operations

Many of the roles for CLEAR TEST can be provided by existing staff performing flight operations, 

payload operations, and logistics. Such roles are performed today for the ISS by the Logistics and 

Maintenance office, the ISS Mechanisms and Maintenance group (also called Operational Support 

Officers or OSO), and the various repair depots that service hardware for the ISS. The NASA Shuttle 

Logistics Depot (NSLD) and NASA Spacecraft Services Depot (NSSD) indicated that the majority of 

ORU repair activity is performed on units that were found to be faulty during ground processing prior to 

flight. The depots reported that only a fraction of the ORUs repaired are returned flight units that failed on 

orbit. Thus, the NASA depots will have the most recent hands-on experience and are an important asset 

for in-space repairs. In most cases, the original vendor will provide the most in depth understanding of the 

electronics ORU at the component level and, thus, will be needed to support the development of 

component-level repair processes.

4.2 CLEAR Operational Concept and Architecture

This section presents a proposed CLEAR Operational Concept and System Architecture. This 

architecture can be applied to electronic repair needs of missions in Earth orbit (via the ISS), the Moon, 

and Mars. The CLEAR Operational Concept responds to the repair needs documented in Sections 3.2 and 

3.3. The CLEAR System Architecture is composed of an Earth and a Space segment (Figure 6). The Earth 

segment is referred to as CLEAR Tele-Operations Engineering Support Team (CLEAR TEST) and

primarily involves the remote support and control of the space segment via telecomunications. The 

ground-based CLEAR TEST center will be similar in concept to the various science payload operations 

centers available today. The space segment involves a combination of manual and semi-automated 

diagnostics, repair, and test capabilities. The space segment hardware is collectively referred to as the 

Semi-Automated Repair and Diagnostic Apparatus (SARADA).
NASA/TM—2010-216784 14

Figure 6.—CLEAR is composed of an Earth segment and Space segment that is linked via 

Constellation Command, Control, Communications and Information (C3I) infrastructure.

CLEAR System Architecture provides four capabilities: 

(1) Tele-operations

(2) Control and Data 

(3) Diagnostics and Test

(4) Semi Automated Repair and Diagnostic Apparatus. 

The CLEAR System Architecture capabilities span the Earth and Space segments via the Constellation 

Command, Control, Communications, and Information or (Constellation C3I) infrastructure.

4.3 CLEAR Earth Segment: CLEAR Tele-Operations Engineering Support Team

4.3.1 CLEAR TEST: Diagnostic, Repair, and Test Process Application Development

Effective response to problems requires access to detailed design information and an understanding of 

the system history and its current configuration. The response also requires the ability to access, 

understand, and use the technical repair tools. The CLEAR TEST will need an array of information and 

an array of technical options to formulate corrective action. The development of a diagnostic, repair, and 

test process will involve not only the design details but the emphasis on tele-operations and remote 

control will require additional data and special tools, particularly if robotic equipment is used. The 

following sections briefly describe the database, library, and development tools depicted in Figure 7.

4.3.2 Vehicle Master Database (Spacecraft Design Data)

For shuttle and ISS, design details are captured in a design database called the VMDB. Diagnostic, 

repair, and functional tests will require detailed design and configuration information. To facilitate 

diagnostics, repair, and functional tests, the VMDB can be expanded to include as-built and as-repaired 

configurations.
NASA/TM—2010-216784 15

Figure 7.—CLEAR Diagnostic, Repair, and Test process development. PRACA, Problem Reporting and 

Corrective Action.

4.3.3 PRACA Database (System Problem History)

The PRACA (Problem Report and Corrective Action) system provides information regarding ongoing 

open-problem reports and historical closed-problem reports. PRACA reports often refer to failure analysis 

reports that may involve a very detailed investigation and examination of a problem’s root cause. The 

PRACA system is very important not only as a problem archive but as a problem-reporting and tracking 

tool. The first time a problem is detected, a problem report is activated. From a CxP perspective, a 

problem report initiation will be the first indication that a CLEAR diagnostic repair and test process is 

needed. The problem report closeout will be the final indication that the CLEAR process is complete.

4.3.4 CLEAR Reference Database

A complete design database is necessary, but not sufficient, to serve all the information needs for the 

CLEAR task. A distinctly new data library is also required. Design databases may provide extensive 

information on acceptance test parameters and functional tests, but they do not generally contain 

information on specific repairs or diagnostic procedures and techniques. Diagnostic and repair procedures 

are usually generated on an as-needed basis. The CLEAR reference database will contain information 

unique to CLEAR System Architecture operations and capabilities. For example, circuit cards 

characterization information for “known-good” boards. The CLEAR reference database is composed of 

information not found in the design database or spacecraft problem reports. 
NASA/TM—2010-216784 16

4.3.5 CLEAR Application Development Tools

The CLEAR System Architecture is expected to have significant tele-operations and will therefore be 

software intensive for both diagnostic and repair operations. Each repair will have unique hardware and 

software setup needs. Planning and subsequent programming of robotic and instrument equipment must 

not consume limited crew time or tie up communications bandwidth. Ground-based engineers will 

conduct programming to set up equipment to minimize crew time. Therefore, CLEAR application 

development tools also will be made available to engineers to develop diagnostic, repair, and test 

programs offline. The resulting diagnostic and repair programs will become part of the CLEAR process 

library which is discussed later.

4.3.5.1 Tele-Robotic Application Tools

These tools are aimed at programming the Space segment to perform various diagnostic and test 

functions for specific circuit applications. Since diagnostics and functional testing involve many of the 

same instruments, they will require the same development tools. In some cases, the programming 

involves purely electronic functions while others, such as automated probing, involve robotic motion 

control. The motion control parameters will be based on circuit computer-aided design (CAD) data for 

component location and identification and to locate registration points. Imaging development tools will 

allow users to develop routines to check CCA registration alignment and control the remote visual 

examination process.

4.3.5.2 Diagnostic and Test Application Tools

Diagnostic and test functions will rely on a new generation of “panel-less instruments” minimizes 

space and weight by eliminating displays and adjustment knobs and by employing a common laptop 

computer as the user interface. Setup of instrument parameters and coordination between stimulus signals 

and signal measurement must be programmed into the hardware. Analog Signature Analysis (ASA) and 

Complex Signature Analysis (CSA) Programming both rely on data from “known good boards.” Similar 

to the U.S. Navy “gold disk” program, these “gold signatures” will be needed to support the diagnostics

(Figure 8). If not available, a library of gold signatures will be acquired through actual tests of good 

circuits performed at a ground-based depot. These will be added to the CLEAR reference library for 

future reference.

Figure 8.—Analog Signature Analysis (ASA) requires extensive characterization of “known good” or 

“Gold” circuit data. Such data is must be archived and managed but the result is an easy to use 

diagnostic tool that allows even an unskilled user to diagnose a circuit in space. 
NASA/TM—2010-216784 17

4.3.5.3 Synthetic Instrument (SI) Application Tools

Synthetic Instruments technology provides a versatile but compact instrument capability. This is 

described further in the diagnostics and test architecture. In many ways, synthetic instrumentation is based 

on the premise that many instrument functions are digital or can be performed by digital circuits, which 

implies that instrument functions can be operated as software. To achieve instrument-level performance, 

it is necessary to embed software into field-programmable gate array (FPGA) that allows designers to 

exploit data pipelines, parallel processes, and other signal processing techniques that give conventional 

instruments their high performance. A set of tools will be needed to create an instrument model and then 

perform the hardware programming. Ground-based simulators of the flight hardware will be needed to 

develop and validate the code.

4.3.5.4 Low-Gravity Reflow Application Tools

Solder Reflow is used for removing components and installing new components. The process 

typically employs a solder paste with heat-activated flux. A predefined temperature profile is required to 

ensure proper flux activation and solder reflow, yet it minimizes the excess temperatures that may damage

the circuit. Solder repair processes may have a dependence on gravity where voids in metal solder joints 

are more prevalent than 1-g and require certain adjustment to the process. Gravity also eliminates normal 

buoyancy driven convection which alters the thermal behavior of the process. To account for gravity 

effects the reflow thermal profiles developed in normal gravity will need to be adjusted for reduced 

gravity. Therefore, reflow modeling tools will include low-gravity effects to adjust heating profiles to 

assure a reliable repair and prevent circuit damage. 

4.3.6 CLEAR Integrated Validation Tools

Before complex commands are uplinked to the Space segment, the code must be validated. The 

complex interactions among the instruments, robotic hardware, flight crew, and repair targets involve so 

many details that it is easy to overlook a detail that results in damage to hardware or injury to a crew 

member. Industry uses development tools that can also perform simulation and serve as an initial 

validation of the process. However, the interaction between robotics, instruments, and crew members will 

require a simulation of the overall process. If substantial crew interaction is required, then a live 

simulation using a high-fidelity mockup of the system will be needed. The simulator and/or trainer would 

support this simulation and also serve as a trainer for flight crews.

4.3.7 CLEAR Repair Process and Uplink Products

The final products of the CLEAR development and validation effort are primarily software to 

configure and control hardware as well as acquire data. For specific ORU and subassemblies, palletized 

repair component kits could be preassembled and stored in stowage. Most repairs will consume only a 

few pieces of any repair kit and could be replenished on an as-needed basis.

4.3.8 CLEAR Process Library

The CLEAR process library represents the accumulated knowledge for the diagnostics, repair, and 

test of circuits. Unlike other databases, this library is intended to contain reusable control codes and setup 

parameters. Much like an industrial CNC library, it will contain the programming code and parameters for 

specific component-diagnostic and repair operations. Because diagnostic processes search for an 

undetermined cause, a variety of diagnostic routines may be used to determine a specific fault. Over the 

life of the circuit design, multiple independent faults may occur. Therefore, we expect to accumulate a 

large library of diagnostic routines. Likewise, a procedure may be needed for every repair of a given 

component type. Therefore, like diagnostics, a significant library of repair procedures can be 

accumulated. Finally, a delta (subset) of acceptance test procedures will be used to verify that the circuit 

has been successfully repaired. It would be useful to have a template process that covers setup operations 

and contains commonly used processes. Should a similar fault reappear, a great deal of effort will already 
NASA/TM—2010-216784 18

have been captured. Over time, the number of team members required can shrink as the library grows and 

experience makes the team more effective.

4.4 CLEAR Space Segment

4.4.1 CLEAR Tele-Operations

Regardless of the repair method (manual or automated), it is essential to define space and groundbased activities related to the repair process and the telecommunications infrastructure that links them.

Repair is an off-nominal or contingency operation and there may be considerable risks to the crew and 

mission. The wide diversity of systems makes it impractical to have each crew member familiar with the 

level of detail required to diagnose and repair flight hardware. The crew must be backed by ground-based 

expertise and a knowledge base capable of resolving the problem, creating and coordinating crew 

procedures, and programming equipment to execute corrective actions. Historically, NASA has 

augmented the flight crew by employing extensive telemetry, communications, and monitoring of 

systems by mission operations centers. Science payloads have been supported by remote payload 

operations centers that provide access to science instruments and experiment payloads, without adding a 

burden on the primary flight system operations. 

The CLEAR Tele-Operations concept is also intended to minimize dependency on real-time 

interaction. Real-time interaction would be feasible for some operations. However, the process of 

diagnosing faults, testing, and setting up a repair is prone to long pauses while support staff assess data 

and consider the next step. Considering the high value of both crew time and communications, it is more 

practical to perform as much of the process offline as possible. Similarly, microgravity experiments 

aboard the space shuttle and ISS were extensively preplanned and automated with optional breakpoints in 

the experiment procedures to accommodate changes based on near real-time assessment of experiment 

data. The CLEAR Tele-Operations is envisioned to operate in the same manner as a Tele-Science Center 

to minimize operational costs.

CLEAR Tele-Operations will operate the flight hardware in manner frequently used in flexible 

automated equipment commonly used in short-run manufacturing operations. To compensate for the high 

cost of labor, manufacturers leverage machinist skills by capturing machine operating parameters as 

special CNC (computer numerical control) code files. The CNC machinist no longer manually operates 

the machine tools but instead creates a script-like program of simple and compact machine “G-codes” that 

instruct the machine to load specific tools, position the work piece and execute machining operations in 

manner similar to what a manual machinist would perform. Although the machining process is automated, 

part mounting, tool loading, machine alignment, and consumable resources are all handled by a manual 

set up. On occasion the automated operation has preprogrammed pauses to allow the machinist to check 

progress and inspect the hardware. Thus CLEAR operates in a similar “semi-automated' manner. The 

primary difference is the programming will be performed on the ground by the CLEAR Teleoperations 

Engineering Support Team and not the flight crew. 

The mechanical portion of the CLEAR SARADA, shown in Figure 9 configured in a repair mode,

will be designed to accommodate both manual and automated operations and provide repair, along with 

diagnostic and test probing capabilities. For the most part, CLEAR SARADA will not operate under 

remote real-time control. Programming and subsequent verification will be performed offline and will 

avoid unnecessary consumption of crew and tele-operations time. To provide efficient preprogrammed 

control and to accommodate flexibility, CLEAR TEST engineers will develop and verify prescripted 

diagnostic and repair routines that may include decision branches at key points.

4.4.2 CLEAR Control and Data

The CLEAR Control and Data (CC&D) system architecture serves as the data backbone of the Space 

segment. The CC&D system must provide for incremental development of the repair-related technologies. 

It must be established early and yet resist obsolescence. A local-area network (LAN)-based architecture is
NASA/TM—2010-216784 19

Figure 9.—The mechanical portion of the semi-automated Repair and Diagnostics Apparatus 

(SARADA) also requires process containment to protect the crew cabin environment.

inherently an open architecture, less restrictive than proprietary architectures, and considered the best 

option for long-term stability. The LAN-based data backbone is consistent with a plug-and-play approach 

that provides ease of integration and incremental growth.

Figure 10 shows many major SARADA functions and illustrates the interconnections where 

commands, data, and power flow. The CC&D controller is both the main controller and master of the data 

network or data backbone of the system. This backbone function is essential to the incremental 

development strategy and must be defined explicitly prior to incremental hardware development. The 

CC&D controller is also the gateway for tele-operations. Each block in Figure 10 has a smart subsystem 

controller that also provides network interfaces to the block above and below it in the system hierarchy. 

Ideally, the blocks would provide a plug-and-play capability that would allow additional blocks to be 

added without requiring a massive reconfiguration of the system. The best way to accommodate plugand-play is with LAN protocols.

The CC&D controller is linked with the spacecraft’s Command and Data Handling (C&DH) network. 

The channel on the spacecraft side would be the branch of the C&DH system that supports payloads. 

Using payload channels, instead of primary system channels, eliminates the concern that CLEAR 

transactions would consume bandwidth needed for mission support. Since the payload command and data 

channels pose no risk of system hardware interference, the CLEAR TEST center can operate 

independently.
NASA/TM—2010-216784 20

Figure 10.—Functions of the Semi-Automated Repair and Diagnostic Apparatus (SARADA).

The crew will interface the system through an available laptop computer. The crew interface may be 

used for monitoring the CLEAR process, archiving instrument data, and performing data processing 

required to analyze and display data. The crew interface will provide the graphics display for CLEAR 

process setup and operating procedures. The crew interface will provide a CLEAR process library that 

will include background information and refresher training for the crew. The crew interface also will 

provide the crew with an override authority to interrupt or halt CLEAR processes and will provide an 

emergency stop function for the crew.

Other key components of the CC&D are the controllers for imaging, diagnostic and test functions, 

and the repair apparatus. These functions are described more in the sections below.
NASA/TM—2010-216784 21

4.4.3 CLEAR Diagnostics and Test

The CLEAR Diagnostics and Test (CD&T) system architecture provides instrumentation for diagnostics 

and test. Diagnostics is used to determine and isolate a system malfunction to the component level and 

determine the root cause. Testing (functional) is aimed at verifying that the repair has restored full function 

and verifying that the repaired assembly is suitable to return to service. Although diagnostics and test are 

different activities, they often use similar functions and the same instruments. Thus, diagnostic functions 

and test functions are considered as simply different applications of a single CD&T system.

Due to payload constraints the allocation of size, weight, and power for diagnostics is expected to be 

much smaller than typical automated test equipment that may occupy multiple racks. Instead of racks, an 

accommodation equivalent to single drawer (0.2 to 0.3 m3

) is more viable. This rules out building as 

systems form conventional bench top instruments. CLEAR Diagnostics and Test architecture considers

strategies that will pack as much capability into drawer space as possible. Synthetic Instruments is an 

approach that the Department of Defense (DoD) has invested in. Described in more detail in technology 

development section, the approach seeks to minimize equipment by employing technologies that allow 

the user to “synthesize” instruments on demand. Synthetic Instruments is expected to be software 

intensive and this means that SI applications can be developed and stored in memory and called up when 

needed. This also means specific circuits diagnostics and tests routines will be uplinked code rather than 

launched equipment.

For initial fault isolation that also minimizes crew demands CD&T will exploit Diagnostic Signature 

Analysis techniques. DSA uses an intuitive graphical comparison technique that expands on the U.S.

Navy's success in with Analog Signal Analysis. Described in the technology development section, this 

approach should allow crew members with relatively low electronic diagnostic skill to successfully 

diagnose and isolate electronic faults.

Functional tests requires a wide array of measurements, external power, and emulation of external 

system interfaces. To the extent possible SI will also provide emulation support for low power external 

signal emulation. Equipment like load simulators are a serious threat to CD&T size and mass. To support 

tests requiring massive loads CLEAR is considering methods that will allow electronics to be tested by 

tying into parent system. Special smart interface devices may be used to act as in circuit interrupts or 

isolators in case a faults that threaten the system

Imaging is essential for examination, process control, and post-repair evaluation. Imaging data 

usually demands high data rates and mass storage. A separate imaging controller provides dedicated 

circuits that minimize the impact on control loops and other instrumentation. Although there are a variety 

of imaging devices potentially available from visible light to infrared (IR) and even x-ray, this system can 

be used to convert images to a common digital format.

4.4.4 CLEAR Repair Apparatus

Component-level repair may be performed manually and will always be an option when human crews 

are available. Development of manual repair capabilities by the CLEAR team are further discussed in 

Section 4.0. However, many repair operations are best handled by dedicated preprogrammed equipment 

designed to reproduce many of the conditions used in manufacturing. A fully automated process such as 

in manufacturing requires special fixtures and equipment, along with a great deal of experimenting or 

system “tuning.” For single unit repairs, a mix of manual and automated operations is more practical and 

is most likely to achieve successful repairs within the spacecraft weight and volume constraints. Certain 

operations, such as wiping away process residues, are simple if performed manually but can be very 

difficult to accomplish by robotic means. Heating devices to narrow temperature bands and then quickly 

and precisely placing them demand automated operations. Semi-Automated repairs reduce the demand for 

high skill while increasing productivity.

The CLEAR Repair Apparatus (CRA) system addresses the repair processes that are beyond the 

capability of manual tools and the crew skill level. The CRA borrows heavily from industry experience 

with automated and robotic technology. Figure 9 shows the SARADA configured in a repair mode where
NASA/TM—2010-216784 22

a reflow system is integrated into a Cartesian robot for positioning. Reflow heat may be delivered as hot 

gas or as IR radiation, or use a combination of both. The CRA architecture is intimately tied to the CTO 

architecture for operations.

In addition to reflow hardware which uses varied combinations of motion and heat application, other 

automated processes would include various other repair needs. This includes the manipulation of 

diagnostic probes which may be may be passive meter or scope probes or they may be actively injecting 

signals for DSA applications. Imaging cameras will support visual examination and process monitoring 

needs. The imagers will be used in setup to locate key registration points and check the alignment of the 

target circuit with the repair apparatus. The camera to ride along on a tool handler as seen in commercial 

probing stations and certain pick-and-place machines. Many of the tasks and tools used in manual repair 

will need to be duplicated for semi automated operations. Motorized rotary tools for drilling, cutting, 

grinding, and cleaning are safer and more precise if performed robotically. For example, using rotary 

tools to remove conformal coatings without damaging the underlying circuit requires a rigid tool handling 

carriage and precise depth control. Finally, automated pick-and-place is important for accurate placement 

of components. Component pallets present the components for easy pickup by the pick-and-place 

component handler.

Repairs performed by manual or automated means will benefit from proper staging of the hardware. 

Tools used by the tool-handling robotic mechanism need to be staged in pre-assigned positions so that a 

robotic mechanism (or human) can quickly locate them. Unneeded items will have to be kept clear of the 

work area. Since space will be limited, components, tools, and materials should be palletized so that they 

can be placed in the work area quickly and removed quickly.

Throughout the repair process, there are operations that create debris, vapor, and smoke. A basic 

glovebox containment will suffice for most applications. The majority of solid debris and vapors can be 

controlled by circulating the air through filters. Filters however, are consumables so processes must 

minimize debris and vapors. Containment of the small amount of cleaning and rinsing liquids can be 

controlled by using saturated wipes. The containment shown in Figure 9 also will include glove ports for 

manual operations. On ISS, there are existing glovebox facilities such as ISS Microgravity Science 

Glovebox (MSG). The CLEAR SARADA could be simplified to fit into a glovebox and minimize the 

overall up-mass required. It is likely that the lunar facilities also will have similar glovebox containment 

available.

5.0 Progress Towards Development of Component Level In-Space 

Electronics Repair

5.1 Incremental Development

The CLEAR project objectives imply providing a NASA depot-level capability squeezed into the 

constraints of a spacecraft in a remote environment with no direct precedence. There is an array of 

technologies and techniques to consider, and an innovative approach is needed to render them compact, 

lightweight, and compatible with space. Some requirements can be addressed by analysis and tradeoff 

studies. Innovative, but untested, techniques will require analysis, lab work, and low-gravity tests to 

validate them for space.

With no accurate way to predict which circuits will need repair, there is a tendency to cover every 

possible repair option. This would result in a project with huge development and coordination costs, as 

well as, a long requirements-definition phase and development contracts. Program managers will attempt 

to contain cost by pushing an aggressive schedule and selecting low-risk off-the-shelf technology. The 

resulting product could be a collection of technologies that is a poor match with the operational 

environment and poorly understood by its users. If users find equipment to be unwieldy, it will provide 

very limited utility.

Operational experience will reveal the failures and the diagnostic, repair, and test needs. Experience 

also will provide the opportunity for an appropriate mix of crew, robotics, and tele-operations capabilities 
NASA/TM—2010-216784 23

to evolve. Incremental development will accommodate the development of techniques with varied levels 

of complexity. Therefore, it is essential to capture “low-hanging fruit” with early flight experience, such 

as manual soldering methods from Station Development Test Objectives (SDTOs) aboard ISS. More 

challenging and complex repair methods that involve automated or robotic solutions will have a longer 

time to evolve.

A system engineering approach that focuses on CxP objectives is needed to assure that the end 

product meets the program needs. Semi-automated repair, diagnostic operations, repair, and functional 

test will depend on ground support and tele-operations. These tasks will be more complex than simply 

building an isolated apparatus. Thus, the overall CLEAR System Architecture is intended to be developed 

as a series of technology packages. The last package must be compatible with the first package. The 

initial flight package must include tele-operations and the data backbone architecture of the system. This 

requires that decisions for this data backbone must be made at an early stage of development.

Because of the long development cycle and the continuous advances in data system technology, the 

CLEAR System Architecture must anticipate obsolescence to ensure long-term viability and minimize 

life-cycle cost. The CLEAR System Architecture will employ two approaches to combat obsolescence: 

(1) a local area network will be the data backbone of the system and (2) an evolving technology called 

synthetic instrument (SI) will be exploited.

As with ISS, CxP will have constraints for payload, crew time training, and communication 

bandwidth. Therefore, tele-operations capability will be developed to fit within existing capabilities. To 

prevent adding operational burden to the program, the CLEAR System Architecture will use the 

telecommunications channels used to support science payloads. This will prevent competition between 

CLEAR and on-going flight operations for high-priority command and control channels

5.2 Reduced Gravity Aircraft Testing

To gain confidence in the reliability of soldering as a standard repair process for space missions, it is 

important to assess the effect of reduced gravity on the soldering process. Prior to the CLEAR project, a 

group of researchers conducted a series of reduced-gravity soldering tests utilizing NASA’s KC–135 

research aircraft. The work, which began in 2001, involved 8 flight weeks of testing and spanned over 

3 yr (Refs. 13 to 17). The primary repair configuration investigated used a plated through-hole (PTH) 

configuration. Results of these tests characterized changes in the solder joints, including geometric 

changes and increases in internal porosity, which can increase by as much as a factor of 3, as a result of 

the reduced gravity environment. The sources of the increased porosity appear to be flux vapor which was 

trapped in the molten solder, and entrapped moisture in the circuit board itself. Several techniques were 

tested to mitigate the porosity increase, including alternate techniques for flux application and 

demoisturization of the circuit board prior to soldering.

Continuing this previous work, the CLEAR team conducted a series of solder tests aboard NASA’s 

new microgravity C-9 reduced gravity aircraft. This work included the examination of various solder and 

flux combinations, most focusing on the use of no-clean or water-clean fluxes with eutectic solders, in 

preparation for an ISS experiment investigating soldering (see Section 5.3). The analysis included

discriminating between samples based on the quality of the reduced gravity environment as well as the 

quality of the solder joint based on NASA standards. Acceptable samples were nondestructively analyzed 

for void formation. Results from this work were presented elsewhere (Ref. 11) but were consistent with 

results from previous testing. These results will help develop criteria for selecting solder, flux, and 

techniques to be used for in-flight repair of electronics.

5.3 Recent Spaceflight Experiments

As discussed previously in Section 3.2, the ISS has available a basic soldering kit, tools, and 

workarea which can be used for some simple repairs. Augmenting these existing ISS tools with additional 

repair tools, the CLEAR project conducted two space-flight experiments aboard the ISS to investigate and 
NASA/TM—2010-216784 24

demonstrate component-level repair. The first experiment, called Soldering in Reduced Gravity (SoRGE), 

investigated the basic processes of soldering in a microgravity environment in a through-hole 

configuration. This experiment built on the results of the reduced gravity aircraft testing described in 

Section 5.0. The second experiment, called Component Repair Exp-1 (CRE-1), demonstrated key aspects 

of the physical processes of end-to-end component-level repair of a circuit board. These include 

conformal coating removal, component removal, board clean-up, and component replacement. Details 

and results of from these experiments are presented elsewhere (Ref. 12).

5.4 Recommendations to Help Enable Manual Electronics Repair

As a result of the spaceflight experiments described in the previous section as well as study conducted 

with the U.S. Navy, the CLEAR team is preparing a report (Ref. 18) that provides recommendations to 

help enable manual replacement of electronics at the component-level. The report discusses the current 

ISS repair capabilities followed by recommendations for future missions. These recommendations include 

hardware and tool requirements, containment options, and crew training. A brief synopsis of these 

recommendations is presented here.

To enable component-level electronics repair in future manned space missions, crews will require 

significantly more capability than currently available aboard ISS. The entire repair process encompasses 

fault diagnostics, the physical repair, and acceptance testing post repair. Additionally, crew members need 

adequate skills based training to be able to respond to wide variety of potential problems. Each area 

(diagnostics, repair, test, and training) requires more capability and forethought to enable future crews to 

conduct repairs in a manner consistent with the constraint of spaceflight. One of the primary constraints is 

that of available crew time. Crewmembers primary mission is to conduct the science and exploration tasks 

assigned. Repairs, although inevitably necessary, should not require the majority of the available crew 

time to conduct.

Fault diagnostic and post-repair functional test concepts are as discussed previously in this document.

These include a combination of increased built in test (BIT) capabilities, signature analysis devices, and 

synthetic instrumentation which can be programmed to meet a specific diagnostic and test need. If a semiautomated system such as the SARADA is not yet available, manual probing (as shown in Figure 9) for 

fault diagnostics would be required. Testing needs would likely be some subset, if any, depending on the 

equipment available for the functions shown back in Figure 1.

For the physical component-level repair, additional tools to those already aboard ISS are required. For 

most repair applications, a higher-end, electronically-adjustable, soldering stations (e.g., those that can be 

adjusted in 1° increments to satisfy the needs of the actual application) is recommended. Furthermore, 

soldering irons which do not require calibration are desired. Should a higher-temperature tip be 

problematic to certify for use in spacecraft, another alternative is a backplane heater (although this 

increases the equipment to be carried). The soldering iron tip does not have to be as hot as in the case 

where the circuit board is at room temperature, because the heater provides most of the energy instead of 

the soldering iron tip. Heating the circuit board with the backplane heater also reduces thermal shock to 

the board by reducing the temperature gradient between the board components and soldering iron tip. The 

available tips in the U.S. Soldering Kit only include one style tips—a screwdriver shape. Smaller or other 

shapes are required to more easily work with many component types including surface mount technology 

(SMT). A number of tools are required to extract solder and maintain the solder extraction equipment 

While the existing ISS IVA Toolkit has a number of hand tools available, most are not suited for use 

in electronics repairs due to size. Smaller electronic components require tools to manipulate the smaller 

components. These include cutters, pliers, tweezers, conformal coating removal tools, lead-forming tools, 

ESD protection, and wire strippers. Fiberglass sticks, dental tools, and even toothpicks are needed for 

removing conformal coating, reapplying conformal coating, or as a tool to position a component on the 

circuit board. The fiberglass in the stick will not wear away as readily, as a wooden stick would, when 

removing conformal coating. The stick will also limit damage due to shorts or static build-up during use.
NASA/TM—2010-216784 25

Other aspects of tools include designs which reduce user fatigue as well as ensuring that the tools are not 

mishandled or used for applications other for which they were intended.

The needed materials and supplies include solder, external solder flux or flux pen, and de-soldering 

wick. If alcohol is used for cleaning or other applications then containment of the alcohol vapors from the 

environment is required. Additional supplies which may be part of a general supply kit include tissues 

(lint-free), toothpicks, and extra fuses. Due to the increases in void defect formation described earlier 

(Ref. 13), an optimum solder chemistry may be recommended pending the results of the SoRGE 

experiment. Note that the 60/40 Rosin Activated (RA) type solder in the current kit is not recommended 

due to the highly active rosin flux core and no way to easily remove the flux residue due to restrictions on 

alcohol use. In general, solders and processes which minimize cleaning such as the use of no-clean flux 

are considered optimal.

The tool recommendations discussed thus far focus on the removal and replacement of electronic 

components. Other electronics repairs may arise which require specialty tools. One example is repairing a 

broken trace or land on a circuit board. Such repairs require the use of a rotary hand tool to excavate 

around the trace or access an internal trace. Tweezers and picks are required to manipulate small 

replacement materials or debris. Furthermore, chemicals are needed to clean or bond replacement parts, 

requiring tools to apply and handle the chemicals. While some tools, such as the rotary hand tool, may be 

available as a part of a general tool kit, most other tools for this or similar tasks will not, and must be 

included in a dedicated electronics repair tool kit. The amount of epoxy required to perform conductor 

repair, both surface and sub-surface, may be too much for the closed environment to handle. As a 

potential alternative, surface conductor repair can be attempted by soldering the replacement in place and 

using the reapplied conformal coating to secure the repair.

The existing containment enclosure, used with the MWA on the ISS, has a number of shortcomings 

that are specific to conducting component-level repair of electronics. The following recommendations 

focus on design considerations for a new containment enclosure. This discussion will also examine visual 

aids which may be included in a future containment enclosure, or as stand-alone instruments with 

applications beyond electronics repair.

Perhaps the single most important recommendation is to have an enclosure which will allow crew 

members to comfortably see and manipulate small parts within the enclosure. Terrestrially, technicians do 

not normally use an enclosure and are typically within 12 in. of the circuit card. With regard to the 

physical characteristics, the containment enclosure should have rigid sides, to avoid problems with 

visibility through the current soft sided enclosure, and a clear window to allow easy viewing of the CCA.

The enclosure should still be collapsible to aid in stowage (although a less setup time would be highly 

desirable as the current design requires at least 30 min for setup). As with the current design, the 

enclosure should have electrics feedthroughs and hole for a vacuum cleaner. The enclosure should be 

sized to accommodate most, if not all, circuit boards a crew member would work on, with enough volume 

to accommodate the soldering tool, board clamp, backplane heater, or other tools and instruments that 

may be necessary.

Visual aids can improve the visibility for the crew while performing a repair. Many of the component 

legs and circuit card pads manipulated in a repair task are small, and working with these small parts may 

be difficult or impossible, and taxing on the crew member, if using only the naked eye. Visual aids that 

can alleviate or eliminate these problems include magnifying lenses, which can be used in a standalone

fashion, as part of the enclosure wall, incorporated in lighting, as a visor the crew member wears, or in 

other ways. Low power microscopes (on the order of 20 X magnifications) are commonly used in ground 

laboratories and workshops, and can be used with the flat sides of an enclosure in a space vehicle or 

habitat setting. Video cameras with macro lenses may also be used to magnify the work area, shown in 

Figure 8 for example, with the benefit of recording the repair session for future analysis. Mission planners 

should include multiple choices among the visual aids as well, allowing crew members to be flexible in 

terms of using the appropriate magnifier for the task at hand, available light levels, transmitting or 

recording video, and personal preference.
NASA/TM—2010-216784 26

5.5 Technology Development Concepts

5.5.1 Synthetic Instruments

Synthetic Instruments (SI) refers to an approach that exploits software and reconfigurable hardware to 

maximize the flexibility of test systems. The motivation behind SI is the need to reduce the size and 

weight of instruments and related hardware used in the diagnosis and test of electronics. It is not 

uncommon for a specific ORU to require multiple racks of equipment. Department of Defense (DOD) 

studies consider automatic test equipment (ATE) as a primary contributor to the high life-cycle cost of 

avionics equipment (Ref. 19). ATE life-cycle cost can become an increasingly expensive part of avionics 

cost over time as hardware becomes obsolete. The studies also determined that test software is a major 

component of avionics and test equipment cost. Hardware and software obsolescence also tends to drive 

up cost, particularly for proprietary systems. These DOD studies prompted development of nontraditional 

concepts for ATE to keep life-cycle cost down. SI is conceived as a way to make ATE equipment more 

universal and easier to update remotely.

SI is implemented on generic hardware, typically Field Programmable Gate Arrays (FPGAs). FPGAs 

are designed to provide a vast array of logic gates that can be configured to provide distinct data and 

control functions. SI is different from virtual instruments, or VI, which employs purely software control 

of digital and analog I/O and rely on computers central processing unit for timing, control, and data 

handling with a significant performance penalty. Unlike software executed by microprocessors, the SI 

programmed into the FPGA executes at extremely high speeds and with high levels of parallel processing.

The FPGA can be reconfigured, on demand, as a completely new SI. The latest generation of FPGAs can 

provide real-time signal processing which was once the domain of digital signal processors. The main 

advantage of SI is that it allows us synthesize high performance instruments on an “as needed” basis.

The strategy behind SI is to allocate any digitized functions to software. Innately analog functions, 

such as sensors, analog signal devices, and power sources are handled by modules that can be 

reconfigured electronically to provide wide operating ranges. In addition, to handle the vast variety of 

connector configurations, SI provides an upfront analog switching matrix that routes signals from a target 

test circuit to a selected analog instrument module. The CLEAR team considers SI (Figure 11) as part of a 

strategy to provide both diagnostic and functional test capability for a wide range of spacecraft electronics 

using only a small amount of physical hardware.

5.5.2 Diagnostic Signature Analysis

Diagnostic Signature Analysis (DSA) is a general term coined to indicate diagnostics by comparison 

of characteristic signatures. Analog Signal Analysis (ASA) refers to a fault finder technique widely used 

by the U.S. Navy for ship board diagnostics. By graphically comparing a test signatures from a faulty 

circuit with a known good circuit a relatively inexperienced technician can quickly identify circuit faults. 

This capability is desirable for flight crews where crew training is focused on mission objectives rather 

than system troubleshooting. ASA however, has limitations, particularly for high frequency circuits. 

Therefore, DSA will likely incorporate a new approach called Complex Signature Analysis (CSA).

CSA is an extends the concept of ASA by exploiting the capability of a vector network analyzer. Not 

to be confused with network protocol analyzers, a vector network analyzer tests networks of components 

in high-frequency signal circuits. Vector network analyzers share certain capabilities with a spectrum

analyzer. These devices are generally used for high-frequency or RF circuits, where operating frequencies 

can range from 10 kHz to 110 GHz.

A vector network analyzer measures the frequency domain properties of component networks rather 

than single components. It injects a signal into the network and measures the signal reflecting back from 

the circuit and the signal transmitted through the circuit. These analyzers are commonly used to test highfrequency amplifiers, filters, and tuning networks and can also test piezoelectric devices like crystal 

resonators. They operate at very low wattage and inject signals into passive networks or active devices 

like amplifiers.
NASA/TM—2010-216784 27

Figure 11.—A synthetic instrument (SI) architecture as a solution to diagnostic and test needs for future 

spacecraft repair capabilities.

For CLEAR, the vector network analyzer provides a complex impedance measurement. Network 

analyzers make their measurements relative to a reference impedance value (typically 50 Ω for RF 

systems). As shown in Equation (1), complex impedance Z is a complex value; that is, it is composed of a 

real value R and an imaginary value X.

Z = R + Xi (1)

The (R) value is the “resistance” term and the (X) value is the “reactance” term and indicates the 

presence of inductance or capacitance in the circuit. Based on complex variable mathematics these terms 

can be combined into a single Complex Impedance value that can be physically measured by the vector 

network analyzer.

Complex impedance measured over a frequency sweep reveals resonant behaviors for both the entire 

network and individual component resonance. By performing a wide sweep, one can identify specific 

components. Despite the complexity of the underlying theory the indentifying a fault by graphical 

signature comparison is relatively easy and by comparing the test signature against a “gold” signature, 

one can quickly spot a failed component.

Figure 12 shows the concept of CSA in which a filter composed of several LC (inductor capacitor) 

nodes has a distinct resonant condition for each node. The plots produced by the network analyzer could 

be used to characterize the network. The actual measurement is taken only at the input end. Note that 

markers 1 through 5 indicate distinct nodes and each node’s contribution to the characterization curve.

Therefore, it is possible to characterize the network without measuring internal nodes. This is particularly 

useful when parts of a circuit are inaccessible. The measurement is taken from the signal injection side of 

the circuit rather than from the output side. In Figure 12, the blue trace is the characterization of a knowngood reference network. The red trace is a test trace from a network where node 2 has a faulty 

component.
NASA/TM—2010-216784 28

Figure 12.—Complex Signature Analysis (CSA)—Each marker indicates a normal resonance of a 

“known-good” network composed of five components. The red trace indicates that element 2 of 

the test circuit has a faulty component and therefore does not match up with the expected 

known-good trace.

In summary, ASA and CSA have similar approaches but measure distinctly different circuit 

behaviors. ASA operates in the time domain, whereas CSA operates in the frequency domain. ASA 

measures the response to a small voltage input like a component tester, whereas CSA measures complex 

impedance, which is a multi-component value that can be analyzed in different ways. The techniques 

have an overlapping range, but one technique does not encompass the capability of the other technique. 

Therefore, ASA and CSA diagnostics are considered to be complementary techniques. The overall 

Diagnostics Signature Analysis technology development will involve the combination of ASA and CSA 

techniques. CLEAR may further refine the capability by developing DSA as a Synthetic Instrument.

5.5.3 Noncontact Diagnostics

The CLEAR team conducted a preliminary feasibility study of noncontact techniques for circuit 

diagnostics. These techniques are intended to address the problems of node access in circuits that are 

protected by conformal coatings. Both ASA and CSA operate by injecting AC signals into the test circuit 

and examining the response. If a probe can be coupled by capacitive, inductive, or RF coupling, it may be 

feasible to inject signals without removing the conformal coating. The capacitive techniques used realistic 

physical parameters (size and materials) for the probes. The RF technique used the same coupling 

capacitance but higher frequencies. Inductive techniques were not pursued because the ability to model 

realistic injection of signals into the card being tested was limited.

The Simulation Program with Integrated Circuit Emphasis (SPICE) was used to simulate the test card 

and faults. For capacitive coupling, a signal was injected relative to a common ground on the circuit being 

1 2 3 4 5

Probe 

point

Input Output

1

2

3

4

5

0

–10

–20

dB –30

–40

–50

0.90 0.95 1.00 1.05 1.10 

Frequency, GHz

2

___Known

good 

- - - Faulty 
NASA/TM—2010-216784 29

tested. The results of the capacitive coupling techniques indicated that the test circuit’s impedance 

dominated the response. The largest effective coupling capacitance that could realistically be achieved 

was less than 0.5 pF. Essentially, this technique is applicable for testing active components and boards 

operating at high frequency, but it is not applicable for low-frequency circuits. The frequency limitation 

of the test method could be removed by allowing differential measurement with dual-probe 

configurations. Although these techniques show promise, additional work will be required to refine the 

methods.

Simulations of capacitive probes show that this technique can be used for high-frequency 

components, such as antennas. However, when there are large inductors or capacitors on the board, the 

common ASA technique seems to be the best option. Unlike capacitive coupling probes, inductive probes 

do not seem to be practical for this application. The size of the inductive probe can be the major limiting 

factor. For inductive probes to be applicable, a board should be designed specifically for receiving these 

probes. Inductive coupling techniques have a strong dependency on the geometry of the board and the 

components close to the trace to be tested. Other electronic coupling techniques such as modulated RF 

coupling should be investigated.

In noncontact analysis, variations in the thickness of the coating layer can cause the analysis results to 

vary significantly. However, collecting reference information from each board for comparison to the same 

board in the future would eliminate the effect of coating thickness variation. This concept would allow 

relative comparison analysis to be applied instead of absolute analysis.

6.0 Summary

NASA’s historical solution to the problem of in-flight electronics repair has been the replacement of 

sub-units called Orbital Replacement Units. This approach requires significant logistical support through 

regular resupply flights. For long-duration space missions, resupply flights are limited. Therefore, NASA 

is investigating component-level repair of electronics as a potential way to reduce the logistical footprint 

required to support future missions. The CLEAR task under the NASA Exploration Technology 

Developments Program’s Supportability project was established to explore how future crews could 

effectively perform electronic repair down to the component level.

To better understand what types of electronic components would need to be repaired, the CLEAR 

team investigated electronic systems to determine the nature of the circuits used during spaceflight.

Component-level repair will involve integrated circuit packaging that is expected to migrate from 

perimeter-mounted through-hole and surface-mount technologies to ball grid and land grid array 

technologies. This trend limits manual solder repair methods to simple discrete devices. High-density ball 

grid and land grid array devices must be repaired using automated techniques. This information was used 

as the basis to develop an architecture that addresses electronic diagnostics, repair, and testing needs, and 

the practical constraints of operating in a space environment.

The CLEAR System Architecture is comprised of an Earth and a space segment. The Earth segment is 

referred to as CLEAR Tele-operations Engineering Support Team which is comprised of system and 

operations experts. The ground-based CLEAR TEST center will be similar in concept to the various 

science payload operations centers available today. The space segment is referred to as the semiautomated repair and diagnostics apparatus (SARADA). The CLEAR System Architecture can allow 

flight crews, within the constraints of a spacecraft or habitat, to:

• Diagnose electronic assemblies and identify the faulty components

• Repair electronics down to the component-level

• Evaluate the circuit post repair via a functional test, and

• Augment the flight crew with knowledge and skills to diagnose faults and perform repairs without 

expanding crew size by a combination of manual and semi-automated processes
NASA/TM—2010-216784 30

In addition, this paper shows results from an analysis that component level repair offers both cost 

benefits and mass savings for extended space missions. Also, this paper discusses recent progress toward 

developing in-space repair capabilities including two space-flight experiments called SoRGE and CRE-1.

Finally, this paper presents technology concepts which could help enable or benefit component-level 

repair. These concepts include developing synthetic instrumentation to meet in-situ testing needs, 

extending Analog Signature Analysis to the frequency domain using an approach called Complex 

Signature Analysis, and finally non-contact diagnostic methods to help diagnose faults without needing to 

penetrate conformal coating.

The proposed approach can increase the flight crew’s ability to act decisively to resolve problems 

while reducing dependency on Earth-supplied logistics for future Constellation Program missions as well 

as the ISS.

References

1. Beddingfield, K.L., Leach, R.D., and Alexander, M.B. (eds.), “Spacecraft System Failures and 

Anomalies Attributed to the Natural Space Environment,” NASA Reference Publication 1390, Aug.

1996. 

2. Rutledge, P.J., Mosleh, A., “Dependent-Failures in Spacecraft: Root Causes, Coupling Factors, 

Defenses, and Design Implications,” Proceedings of the IEEE Annual Reliability and Maintainability 

Symposium, 0149-144X/95, (1995), pp. 337–342.

3. Columbia Accident Investigation Board, “Columbia Accident Investigation Board Report” [online 

report], Vol. 1, Aug. 2003 URL: http://caib.nasa.gov/news/report/volume1/default.html [cited 26 Dec.

2007].

4. Pettegrew, R.D., Easton, J.W., and Struk, P.M., “Repair of Electronics for Long Duration 

Spaceflight,” 45th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, Jan. 8–11, 2007, 

AIAA–2007–1364.

5. Easton, J.W., Pettegrew, R.D., and Struk, P.M., “Electronic Repair Concepts for Long-Duration 

Spaceflight,” 45th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, Jan. 8–11, 2007, 

AIAA–2007–545.

6. Pettegrew, R.D., Easton, J.W., Struk, P.M., and Anderson, E.E., “In-Flight Manual Electronics Repair 

for Deep-Space Missions,” Aerospace Conference, 2007 Institute of Electrical and Electronics 

Engineers (IEEE), Mar. 3–10, 2007.

7. Struk, P.M., Oeftering, R.C. Easton, J.W., and Anderson, E.E., “Semi-Automated Diagnosis, Repair, 

and Rework of Spacecraft Electronics,” 46th AIAA Aerospace Sciences Meeting and Exhibit, Reno, 

NV, Jan. 7–10, 2008, AIAA–2008–1130.

8. Mankins, J.C., “Technology Readiness Levels: A White Paper,” Apr. 6, 1995, Advanced Concepts 

Office, Office of Space Access and Technology, URL: [cited 26 Dec. 2007]. 

9. Tate, J.M., Bartlett, J.K., Robinson, J.A., Maender, C.C., Putcha, L., Smith, S.M., Bowman, M.A., 

Dulchavsky, S.A., Sargsyan, A.E., Miller, S.K., Banks, B.A., deGroh, K.K., and Tsui, D., “Synergies 

between Space Research and Space Operations-Examples from the International Space Station,” 45th 

AIAA Aerospace Sciences Meeting and Exhibit, Jan. 8–11, 2007, Reno, NV, AIAA–2007–547.

10. Grugel, R.N., Cotton, L.J., Segre, P.N., Ogle, J.A., Funkhouser, G., Parris, F., Murphy, L., Gillies, D., 

Hua, F., and Anilkumar, A.V., “The In-Space Soldering Investigation (ISSI): Melting and 

Solidification Experiment Aboard the International Space Station,” 44th AIAA Aerospace Sciences 

Meeting and Exhibit, Reno, NV, Jan. 8–12, 2006, AIAA–2006–521.

11. Easton, J.W., Struk, P.M., and Rotella, A., “Imaging and Analysis of Void Defects in Solder Joints 

Formed in Reduced Gravity Using High-Resolution Computed Tomography,” 46th AIAA Aerospace 

Sciences Meeting and Exhibit, Reno, NV, Jan. 7–10, 2008, AIAA–2008–0824.

12. Easton, J.W. and Struk, P.M., “Current Space Station Experiments Investigating Component Level 

Electronics Repair,” AIAA SPACE 2009 Conference & Exposition, Sep. 14–17, 2009, Pasadena, CA, 

AIAA–2009–6798.
NASA/TM—2010-216784 31

13. Watson, J.K., Struk, P.M., Pettegrew, R.D., and Downs, R.S., Experimental Investigation of Solder 

Joint Defect Formation and Mitigation in Reduced-Gravity Environments, AIAA Journal of 

Spacecraft and Rockets, Vol. 44, No. 1 (Jan.-Feb. 2007), pp. 174–182.

14. Pettegrew, R.D., Struk, P.M., Watson, J.K., Haylett, D.R., and Downs, R.S. Gravitational Effects on 

Solder Joints, Welding Journal, 2003, pp. 44–48.

15. Struk, P.M., Pettegrew R.D., Downs, R.S., and Watson, J.K., The Influence of Gravity on Joint Shape 

for Through-Hole Soldering, 43rd AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, Jan.

10–13, 2005, AIAA–2005–0541 and NASA/TM—2005-213589, 2005.

16. Struk, P.M., Pettegrew, R.D., Downs, R.S., and Watson, J.K., The Effects of an Unsteady Reduced 

Gravity Environment on the Soldering Process, 42nd AIAA Aerospace Sciences Meeting and Exhibit,

Reno, NV, Jan. 5–8, 2004, AIAA–2004–1311 and NASA/TM—2004-212946, 2004.

17. Pettegrew, R.D., Struk, P.M., Watson, J.K., and Haylett, D.R., “Experimental Methods in Reduced 

Gravity Research,” NASA/TM—2002-211993, 2002.

18. Easton, J.W., Struk, P.M., Funk, G.P., Latta, G.S., Ganster, A.W., Estes, B.E., “Recommendations for 

Enabling Manual Component Level Electronic Repair for Future Space Missions,” NASA Technical 

Memorandum, in-preparation.

19. Humprey, R., Addressing future test challenges via synthetic instrumentation, Military Embedded 

Systems, May 2006, URL: http://www.mil-embedded.com/articles/authors/humphrey/ [cited 26 Dec.

2007].
REPORT DOCUMENTATION PAGE Form Approved 

OMB No. 0704-0188 

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the 

data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this 

burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. 

Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB 

control number. 

PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 

1. REPORT DATE (DD-MM-YYYY)

01-09-2010 

2. REPORT TYPE

Technical Memorandum 

3. DATES COVERED (From - To)

4. TITLE AND SUBTITLE

Approach to In Situ Component Level Electronics Assembly Repair (CLEAR) for 

Constellation 

5a. CONTRACT NUMBER

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S)

Struk, Peter, M.; Oeftering, Richard, C. 

5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

WBS 825855.01.03.03.03 

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

National Aeronautics and Space Administration 

John H. Glenn Research Center at Lewis Field 

Cleveland, Ohio 44135-3191 

8. PERFORMING ORGANIZATION

 REPORT NUMBER

E-17412 

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

National Aeronautics and Space Administration 

Washington, DC 20546-0001 

10. SPONSORING/MONITOR'S

 ACRONYM(S)

NASA 

11. SPONSORING/MONITORING

 REPORT NUMBER

NASA/TM-2010-216784 

12. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified-Unlimited 

Subject Categories: 12, 16, 18, and 33 

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

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

13. SUPPLEMENTARY NOTES

14. ABSTRACT

Maintenance resupply is a significant issue for long duration space missions. Currently, the International Space Station (ISS) approaches 

maintenance primarily around replaceable modules called Orbital Replacement Units (ORU). While swapping out ORUs has served the ISS 

well keeping crew time for maintenance to a minimum, this approach assumes a substantial logistics capacity to provide replacement ORUs 

and return ORUs to Earth for repair. The ORUs used for ISS require relatively large blocks of replacement hardware even though the actual 

failed component may be several orders of magnitude smaller. The Component Level Electronics Assembly Repair (CLEAR) task was 

created to explore electronics repair down to the component level for future space missions. From 2006 to 2009, CLEAR was an activity 

under the Supportability project of the Exploration Technology Development Program. This paper describes the activities of CLEAR 

including making a case for component-level electronics repair, examination of current terrestrial repair hardware, and potential repair 

needs. Based on those needs, the CLEAR team proposes an architecture for an in-situ repair capability aboard a spacecraft or habitat. 

Additionally, this paper discusses recent progress toward developing in-space repair capabilities--including two spaceflight experiments--

and presents technology concepts which could help enable or benefit the same.

15. SUBJECT TERMS

Electronics; Maintenance; Soldering; Diagnostics; Space maintenance; Telerobotics 

16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

 ABSTRACT

UU 

18. NUMBER

 OF 

 PAGES

37 

19a. NAME OF RESPONSIBLE PERSON

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

a. REPORT

U 

b. ABSTRACT

U 

c. THIS 

PAGE

U 

19b. TELEPHONE NUMBER (include area code)

443-757-5802 

Standard Form 298 (Rev. 8-98)

Prescribed by ANSI Std. Z39-18