47th International Conference on Environmental Systems ICES-2017-265 16-20 July 2017, Charleston, South Carolina

Lessons Learned Analysis in Thermal Tests for in Brazil

George Favale e Feranandes1a,b, Roy Soler Stevenson Chisabas2a

Osvaldo Donizete3 a, Carlos Frajuca4b, Daniel Fernando Cantor5

aInstituto Nacional de Pesquisas Espaciais - INPE, Laboratório de Integração e Testes – LIT, Av. dos Astronautas, 1758, 12227-010, São José dos Campos, SP, Brazil.

bInstituto Federal de Educação, Ciência e Tecnologia de São Paulo – IFSP, Rua Pedro Vicente, 625, Canindé, 01109-010, São Paulo, SP, Brazil.

Satellite projects include many mandatory and needed parameters and requirements for their proper functioning during their mission. Although there are many orbital dynamics similarities among satellites, dedicated analyses are carried out with the purpose of analyzing all system responses, when they are exposed to the spatial environment. Inserted in a satellite project, or any other kind of component for this application, are the thermal control projects and analyses. Taking into account all those pieces of information, all thermal test specifications are generated and carefully dimensioned. The CubeSats, which figure as experimental spatial systems designed, developed and built by universities and research institutes, with components not 100% qualified for these purposes, should also undergo this dedicated thermal analysis to generate more specific test requirements for each mission and contribute to the increase of the system reliability. However, in most of the cases, that is not what happens. The Integration and Testing Laboratory - LIT, at the National Institute for Space Research - INPE, in São José dos Campos - SP, Brazil, recognized for its expertise in all the assembly, integration and test cycle for satellites and space components and using its experience acquired in over 25 years working in this field intends, in this article, to discuss all lessons learned while performing CubeSats’ space simulation tests, in qualification and acceptance levels. We will discuss topics related to instrumentation, test specification, setup and lack of qualified human resources in projects, among other relevant themes related to thermal tests in CubeSats and, in the end, we will give our final evaluation.

Keywords: Thermal Tests, CubeSat, Instrumentation, Setup, Qualification Level, Acceptance Level

Nomenclature AEB = Brazilian Space Agency AESP-14 = Turma AeroESPacial 14 anti-ESD = anti- Electrostatic discharge Atm = Atmospheric CBERS = China-Brazil Earth Resources Satellite

1 Mechanical Engineer, Integration and Test Laboratory – LIT, [email protected] 2 Aeronautical Engineer, Integration and Test Laboratory – LIT, [email protected] 3 Mechanical Technician, Integration and Test Laboratory – LIT, [email protected] 4 Mechanical Engineering Professor, IFSP, [email protected] 5 Research Engineer, [email protected] CONAE = Comisión Nacional de Actividades Espaciales CRS = Southern Regional Center FCFM = Faculty of Physical and Mathematical Sciences FM = Flight Model GAUSS = Group of Astrodynamics for the Use of Space Systems GSE = Ground Support Equipment H-IIB = H II Transfer Vehicle B HSB = Humidity Sounder for Brazil HTV = H II Transfer Vehicle IGGF = International Geomagnetic Reference Field INPE = National Institute for Space Research ISIS = Innovative Solutions In Space ISS = International Space Station. ITA = Technological Institute of Aeronautics LEO = LIT = Integration and Testing Laboratory mBar = miliBar NASA = National Aeronautics and Space Administration QM = Qualification Model SAC-D = Scientific Application Satellites-D SATEC = Technological Satellite SCD = Data Collector Satellite SERPENS = Sistema Espacial para Realização de Pesquisas e Experimentos com Nanossatélites SPEL = Space and Planetary Exploration Laboratory SUCHAI = Satellite of the University of Chile for Aerospace Investigation TCC = Thermal Climatic Chamber TCT = Thermal Cycling Test TuPOD = TubeSat Deployer TVC = Thermal Vacuum Chamber TVT = Thermal Vacuum Test UFABC = Federal University of ABC UFMG = Federal University of Minas Gerais UFRGS = Federal University of Rio Grande do Sul UFSC = Federal University of Santa Catarina UFSM = Federal University of Santa Maria UHF = Ultra High Frequency UNB = Brasília University VHF = Very High Frequency

I. Introduction FTER more than 50 years since the first space probes were launched, the satellites have developed and Aincreased in size and complexity. This increase has also required the development and specialization of the professionals involved, because at each new project, new payloads, special monitoring and research systems are needed. Over time, there has also been an increase in the demand for Earth’s monitoring information, for weather forecasting, and even for new communication and espionage systems, for example. These initial projects were developed by governmental research institutes that saw satellites as strategic tools and a demonstration of their technological capacity. With the maturing of technologies, other researchers and institutes also began to develop their own projects. Today, satellites play an essential role for modern societies. Private companies have developed to the point where, today, they can commercialize services of launching satellites, probes and people, and even fully assembled satellites, as their customers wish, and which have already been delivered in orbit. The opportunity that was exclusive to big research institutes, private or governmental, is now part of the reality of many students, teachers and researchers around the world, with the creation of CubeSats projects. The short

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development time, reduced size and the use of off-the-shelf components have made these projects an important tool in students’ development worldwide. Many research institutes are also using this strategy to develop experimental payloads and as a trusted platform for acquiring the information needed to develop their research projects. This concept began in 1999 when professors Bob Twiggs, at Stanford University, and Jordi Puig-Suari, at California Polytechnic State University developed the CubeSat concept with the intention of making it possible to use its idea for the development of university students1. Later the CubeSats were standardized in one “unit” (1U) a cube with 10 cm x 10cm x 10 cm and mass close to one kilogram. It can also be set with two units (2U) and three units (3U). With this standardization, it was possible to develop specific deployers that can be used in conventional launchers or in the ISS - International Space Station. CubeSats, as well as any component or equipment for space application, need to undergo thermal tests in order to ensure its operation and performance while fulfilling its mission. Among all the necessary tests are the thermal tests. This type of test is necessary because they can simulate the temperature variations and vacuum pressures imposed by the space environment, and reduce the outgassing rate of the materials and components to acceptable levels, since they are not 100% qualified for this application. In Brazil, these tests are carried out in the Integration and Testing Laboratory - LIT. This paper intends to show and discuss the lessons learned in the thermal tests, in levels of qualification and acceptance, of five projects tested at LIT. To do so, we will bring the information about the laboratory experience and its test facilities used in the tests, a CubeSats’ projects overview and all the lessons learned for performing the tests and, finally, our conclusions.

II. History The thermal tests are fundamental to validate and qualify the Cubesat performance when it is exposed to temperature variations and vacuum pressures imposed by the space environment and also to reduce the degassing rates of the components to acceptable levels, due to the fact that these satellites have been frequently manufactured with components not 100% qualified for these purposes. In Brazil, the thermal tests are performed in the LIT – Integration and Tests Laboratory.

A. Integration and Test Laboratory - LIT The LIT (Figure 1) is one of the laboratories of INPE – National Institute for Space Research, inaugurated in December 1987. It is specialized in all assemblies, integration, and test cycles for space components and systems2. In all its history, the LIT has supplied many of the needs of the spatial programs. Since the beginning of the Brazilian Space Program, the LIT has performed many thermal tests in satellites such as Data Collector Satellite - SCD-1[3], 2 e 2A, China- Brazil Earth Resources Satellite - CBERS-1, 24,5 and 2B, Humidity Sounder for Brazil – HSB6 (meteorological payload developed to equip Satellite - NASA), Technological Satellite – SATEC7, the thermal model test8 and all the Brazilian equipment and subsystems of CBERS 3-4, and the space simulation test of Scientific Application Satellites-D - SAC-D/Aquarius flight model9 (NASA / CONAE).

Figure 1. LIT’s testing hall.

B. CubeSat’s Thermal Test Facilities For the thermal test achievements two TVC – Thermal Vacuum Chamber and one TCC – Thermal Climatic Chamber of Thermal Vacuum and Climatic Test Group were used, at LIT, Brazil. The TCC is 1,000mm x 1,000mm x 1,000mm and is able to perform in a -100°C to 180°C temperature range, having humidity and temperature

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gradient programmable. For spatial devices, a continuous purge of gaseous nitrogen is maintained inside the test chamber compartment in order to avoid water vapor condensation on specimen. Thermal tests in vacuum environment were performed in two different chambers. TVC 250 liters, for the NANOSAT-BR1 and AESP-14 tests, and TVC 1x1meter, for SERPENS, UBATUBASAT e SUCHAI tests. Both chambers work with mechanical and cryogenic pumps capable of carrying the vacuum pressures until 1 x 10-6mBar. They are equipped with a shroud, projected to work with thermal radiation as the main way to temperature changes in the specimen. It is controlled by a thermal system that works with nitrogen (liquid and gaseous) and capable to perform a -180°C until 180°C range of temperature. Moreover, it is important to highlight that all temperature and pressure control systems are calibrated periodically, according to the legislation, the good quality practices Figure 2. CVT 1x1 meter. and reliability.

III. Tested CubeSats Five CubeSats were tested at LIT. In this chapter, each project, developers, specifications, payloads, launcher and results will be shown.

A. NANOSATC-BR1 NANOSATC-BR1 was the first Brazilian CubeSat manufactured and tested. It was developed from a 1U platform, from ISIS, and its mass was close to one kilogram. Its payload was composed of, among other technological and scientific experiments, to study magnetosphere`s disturbances10. During its research and development phase, several students, professors, technicians and engineers were involved and more than fifty documents were published, including speeches, technical articles and reports11. As stipulated by the developing team, two tests were performed on NANOSATC-BR1. The QM was qualified by a thermal test, in atmospheric pressure. A few months after that, the FM was tested, in acceptance level, by a combined thermal vacuum test. At the beginning, a two-hour Burn-In Test was performed and, immediately after that, the thermal cycling test in vacuum was fulfilled. Both tests were performed without any problems before, during or after the tests. The NANOSATC-BR1’s thermal testing campaign finished in March / April 201412,13.

Figure 3. NANOSATC-BR1 and its information about developer, launcher, and thermal test specifications.

NANOSATC-BR1 (Figure 3) was successfully launched on July 19th, 2014, by launcher RS-20, Dnepr , from Yasny Launch Base, in . In operation for over 30 months, CubeSat NANOSATC-BR1 has 4 International Conference on Environmental Systems

succeeded in acquiring data able to prove the prediction of theoretical values of the intensity of the Earth´s Magnetic Field, as predicted by the model of IGGF - International Geomagnetic Reference Field15.

B. AESP-14 AESP-14 (Figure 4) was the second Brazilian CubeSat. However, it was the first developed and made 100% in Brazil. It was assembled in a 1U platform, with mass close to 760 grams, and projected mission life of about three months. AESP-14’s main objective was some students’ technical training, involving all steps in a space project, since the conception and mission design up to its operation in orbit. Its main payload was a Langmuir Probe, developed by the Atmospheric Science Department of INPE. Its intention was to investigate the mechanism of equatorial plasma bubbles, and provide in situ data about atmospheric/ionospheric phenomena13,14.

Figure 4. AESP-14 and its information about developer, launcher, and thermal test specifications.

Two models of AESP-14 were tested: the QM and the FM. For the QM, a thermal cycling test, in atmospheric pressure, was performed with a severe range of temperature and exposure time. To control the lowest level of humidity, a gaseous nitrogen purge was maintained, inside the chamber, during the test. For the FM model. A combined thermal cycling test was performed, in vacuum, the same as the strategy that was applied to NANOSATC- BR1. All functionalities were tested, in both tests, and the CubeSat worked well. The thermal testing campaign was finished in May / June 201417,18. AESP-14 was successfully launched into space on January 10th, 2015, by the launch vehicle Falcon-9 V1.1, SpaceX (Space Exploration Technologies Corp.)19, from Cape Canaveral Air Force Station, Florida – USA, together Dragon’s CR-5 spacecraft. On February 05th, 2015, it was released into space from the ISS. However, unfortunately, no signal from the satellite was received20.

C. SERPENS CubeSat SERPENS (Sistema Espacial para Realização de Pesquisas e Experimentos com Nanosatélites) was another Brazilian CubeSat which was successfully developed and made in Brazil. A 3U size CubeSat, with mass close to 3 kilograms and expected mission life of about six months21, SERPENS was built with two sectors: sector A, responsible for VHF communication and sector B for UHF communication. Both sectors will receive data from several data collection platforms installed in the Brazilian territory, and that information will be available to be relayed to receiving stations on Earth22.

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Figure 5. SERPENS and its information about developer, launcher, and thermal test specifications.

Two models of SERPENS (Figure 5) were tested. To qualify the engineering model, a Burn-In test was performed, in vacuum, with maximum temperature higher than the performed for the flight model. The FM faced a thermal cycling test, in vacuum, with a temperature range smaller than the one used for the other two CubeSats tested before. The tests were carried out without any problems and all tests were finished in March / April 201523,24,25. SERPENS was launched to the ISS – International Space Station, on August 19th, 2015, by the Japanese launch vehicle H-IIB, inside the pressurized cargo supply HTV-5 “Kounotori 5”, from Tanegashima Space Center, Japan. On September 17th, 2015, it was released into space from the ISS. On March 27th, 2016, as scheduled, CubeSat SERPENS reentered the Earth’s atmosphere achieving its developing and workmanship training, space projects integration with international institutions, and the reception, storage and transmit environmental data mission with full success26.

D. UBATUBASAT Picosatellite Tancredo – I is the first UBATUBASAT’s satellite project, from public School “Presidente Tancredo de Almeida Neves”, in the city of Ubatuba – SP, Brazil, with technical support from the Space Engineering and Technology area, at INPE. It was assembled from a tubesat kit, bought from Interorbital Systems. Its mass is less than 750 grams and has 90 days of expected life27. Its payload is composed of a simple voice recorder, developed by the students, and a miniaturized Langmuir Probe, developed by the Aeronomy Department, at INPE28. In accordance with the origins of UBATUBASAT’s project, its team had only one model to be tested. In addition, they had to test their battery, though. The battery worked as expected during the TVT. For the FM, the TVT was performed in vacuum with a temperature range close to the one used for the other CubeSats. CubeSat UBATUBASAT worked in all functional tests and was approved to be launched. The TVT finished in December 2015 shutting down the thermal test phase29,30.

Figure 6. UBATUBASAT and its information about developer, launcher, and thermal test specifications. 6 International Conference on Environmental Systems

UBATUBASAT (Figure 6) was launched to the ISS – International Space Station on December 9th, 2016, by the Japanese launch vehicle H-IIB, from Tanegashima Space Center, Japan. On December 20th, 2016, using the deployer system TuPOD (GAUSS Srl.), it was released into space from the ISS. Currently, the reception of the voice recorder message and the telemetry’s signal prove its full operation.

E. SUCHAI SUCHAI (Satellite of the University of Chile for Aerospace Investigation) (Figure 7) is the first Chilean CubeSat project. It was built in a 1U platform, mass close to one kilogram and mission life of one year and was developed by undergraduate students, engineers and professors of the Electrical Engineering, Physics and Mechanical Engineering Departments of the Faculty of Physical and Mathematical Sciences (FCFM) at Universidad de Chile33. It was the first CubeSat for the University of Chile’s CubeSat program. This program intends to apply all the knowledge learned in the SUCHAI’s development into two 3U CubeSats (SUCHAI2 and SUCHAI3) that are currently in the designing phase in the SPEL – Space and Planetary Exploration Laboratory. The scientific payload is (1) a Langmuir Probe to study the ionosphere in synchronization , (2) an experiment to study the out of equilibrium fluctuations in a hostile environment, (3) an experiment that proposes studying the heat dissipation in electronic components in the space environment, (4) a digital camera, and (5) a battery health management experiment34,35. CubeSat SUCHAI, is available to fly and will be launched in 2017 and will have a polar elliptical orbit 700Km (LEO).

Figure

7. SUCHAI and its information about developer, launcher, and thermal test specifications.

The SUCHAI team came to LIT in two different times. In the first one, they brought a QM that underwent a Bake-Out test composed of two cycles. The test was successfully completed and finished in May 2014. Two years later, a Bake-Out test was performed on the FM and it was tested following the ISILaunch09 procedure36,37. In accordance with this document: “... the purpose of the bake-out test is to reduce to an acceptable level the outgassing rates of flight equipment associated with instrumentation that is sensitive to molecular contamination…”. Following this recommendation, the Bake-Out was performed exactly as it is required38. The Bake-Out test finished in January 2016 and the CubeSat presented perfect operation.

IV. Lessons Learned In this chapter, we will bring all lessons learned performing thermal tests in CubeSat projects described in the previous chapter. For a careful analysis, the lessons learned were shared in seven main subjects and, at the end of each topic, you can see our suggestions to deal with the related problems. It is important to underline that all subjects are related to each other. For example, the problems related to “Instrumentation” are intrinsically related to “Lack of Skilled Manpower”, or other problems connected with “Test Specifications”. Even so, we believe that this way of sharing the subjects will make the organization and understanding easier.

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A. Lack of Skilled Manpower Currently, CubeSats projects show up as important tools in the development of students and research institutions. When these CubeSats projects are compared to big satellite projects, the requirements at each stage of their development turn out to be remarkably reduced. Even though, the design, material selection, fabrication process, and test campaign need careful attention. To guarantee the spacecraft and its payload success, extensive ground tests are carried out. In this way, the thermal tests are able to, at least, realistically simulate the environmental conditions that the satellite will encounter during its mission39. There are three main motivations for conducting thermal tests in CubeSats: the components and subsystems qualification in development phases, for subsystems acceptance already built in flight model and compliance with a prerequisite required by the launcher. In this way, when planned and performed correctly, each thermal test can and should provide important information to its developers. It is a fact that CubeSats university projects rely on reduced teams, limited infrastructure, low budget and little experience of the participants in space projects. Some situations that may further aggravate the problems related to the lack of skilled manpower in space projects are the lack of experience in managing work teams focused on research and development projects, inefficient hierarchical regime and centralized decision making have proved to be serious and recurrent problems faced before, during or after the tests. A widely-used tool in the development of big satellites that could be applied to CubeSats projects is the use of dedicated models and thermal analyses. These tools consider information and projections related to orbit, altitude, mission, and others, and analyze each possibility to ensure that the environment does not compromise the mission and its components operate in appropriate temperature ranges39, as estipulated by the thermal control system. Unfortunately, the practice of building a thermal model for CubeSats is still not a habit. It is true to say that simplified systems (CubeSats) would generate simplified and yet reliable models40,41 and would require a relatively specialized workforce. Our observations show that some of the projects tested did not use this analysis tool. This observation is possible because important information for the comparison between the analytical model and the information obtained with the test was neglected. During a thermal test, some functional tests are necessary to simulate certain situations that the satellite may face during its orbital life (operation in safe mode, start at low temperatures and sending and receiving information, for example). These situations are simulated in the analytical model and the results are then compared to the results obtained during the tests. In some of the thermal tests performed, the CubeSat’s functional tests were simplistic and would not provide relevant information for a quality comparison with the thermal model results, if it existed. And yet, any real system analysis of performance was performed by summarizing the pass/fail criteria just for whether the system worked. Other problems, such as the team's lack of knowledge regarding the purpose and the appropriate methodology for the test, the lack of test monitoring, are examples of the developers’ poor preparation. Also, the absence of the environmental test specification, with accurate and necessary information happened in more than one opportunity. Certain attitudes such as a more careful bibliographic review, directed studies, participation in courses, congresses and seminars could cooperate with the solution to these problems. The amount of available material for consultation could help the developers, and their team, to enrich the project. Process standardization could also help in reducing systematic errors, still in their development phase. We understand that all development cycle of CubeSats should be multidisciplinary. In this way, the development of a coordination team with teachers from various interest areas and the delegation of responsibilities to the staff leader of each team could reduce the problems related to the decision-making centralization and could increase the project development dynamics. The elaboration of this team would also contribute to the reduction of workmanship problems as long as the selection of the students assigned to each activity takes into account their affinities and possible contributions. Moreover, the authors agree that some of the problems may in the future cease to exist. This is because many CubeSats projects, developed so far, have only completed the construction and launch phase of a first model, which is part of a larger project with more CubeSats (as is the case of the CubeSat SUCHAI42 project). Thus, assuming that all projects should have their own "lessons learned" and, these lessons will help developers not to make the same mistakes on other satellites.

B. Test Specification There are two main initiatives for conducting a thermal test. The first refers to the need for confirming and validating the satellite's thermal control system, and the second to the need for assessing the components and equipment integrity, manufacturing and assembly processes as individual units, and the satellite. For this purpose, documents related to test specifications must be carefully produced. 8 International Conference on Environmental Systems

These documents are essential for the test performing following the parameters and characteristics designed by the developers. All this caution is necessary because, from these tests, important information for the feedback of the thermal models will emerge, and in some cases, of the components performance, equipment, subsystems or of the space vehicle itself43. In this case, some developers did not prepare documents coherent with the work to be done. Information regarding the methodology adopted for the tests, the position and quantity of the thermocouples for the temperature data acquisition, the setup inside the chamber, the need for power supply, the limit temperatures of the components for the definition of test’s abort criteria (temperature which, if reached by an analyzed component or subsystem, is able to abort the test for verifications), description of the critical points, pass / fail criteria, are some of the pending information. In some cases, no test reference document was even prepared. All these reasons underscored the low attention of the developers with the production of a complete and functional test specification. It is LIT’s practice writing a complete test procedure, before the start of the test, with all the information necessary for its accomplishment. This practice comes from the fulfillment of a requirement of the space programs that INPE / LIT are involved in and the Quality Control Department applied for spatial tests. No differentiation is made between testing of big satellite programs and CubeSats and all measures to ensure the quality and safety of the tests are taken. The composing of this test procedure24,29,37 has as its main reference document the "environmental test specification" document provided by the customer/developer23,31,32. These documents contain information on the chamber to be used (which is the vacuum-thermal or climatic chamber, its specifications and information, capacity, size, among others), the data acquisition system configuration, about the specimen under test and its configuration (quantity and positioning of thermocouples, power supply, the chamber’s setup, maximum and minimum temperatures, time of exposure, among others)39. It is also part of the procedures adopted by the laboratory to hold a meeting before the start of each test. The lack of these procedures, by the developers, ends up causing delays in the test schedule because, this meeting, needs to be realized more than once and the necessary information reunited. There are also delays in assembling instrumentation in the CubeSat, in preparing power supply systems for functional tests, setting up the data acquisition system, the CubeSat setup inside the chamber and finally the beginning of the test. In the author’s opinion, a more careful analysis by the developers could correct this problem. Several documents related to satellite and CubeSats test specifications are available in the current bibliography, as well as bibliographies of the essential data to be contained in these documents44. As discussed in the previous item, the development of teams responsible for certain decisions and development phases of the CubeSat could cooperate to solve this problem, since a certain team could be responsible for the necessary tests and, consequently, for the procedures and organization thereof.

C. Instrumentation All components and transducers installed and the data acquisition systems (temperature, pressure, current, voltage, power, vibration, for example) required to control and manage the test are defined as instrumentation. This information is essential for the proper performance of any test (not just the thermal tests). Thus, the thermal test planning must consider all the necessary instrumentation for its correct execution39. The development cycle of big satellite subsystems encompasses careful analysis and design, because of its complexity, cost, special components, strict quality control and a highly skilled workforce. All the critical points are analyzed and will show the information about the sensitive points that will require instrumentation for the thermal test. This information is also necessary for the spacecraft thermal model because they tell the developers the thermal power dissipated by the equipment in full operation, for example. Every large satellite project has its dedicated thermal model. This information serves to show the satellite thermal distribution and to assess whether the thermal control systems will perform their mission properly. In the case of CubeSats, the great question is: what is this source of information, since many of these projects do not have their own thermal models or adequate thermal analyses of their subsystems? How to analyze and compare performance information if, in many cases, any functional test is predicted during the thermal test? In our assessment, these questions have only one answer: careful analysis of all subsystems. As already suggested in the previous item, team organization, with responsibilities shared, and the decentralized decision-making could help to solve some problems. So a particular team responsible for developing a payload provides all the technical information necessary to make its subsystem qualification and acceptance decisions. Although many CubeSats projects are undertaken by inexperienced students and teachers, the lack of careful analysis is not justified. The picture gets worse when experienced contributors do not pay attention to this problem.

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As a result, tests with undersized instrumentation are performed, and the subsequent analysis of these data does not show the real interaction between CubeSat and the test environment. To further illustrate this problem, a description of a real situation follows: Shortly before the start of the instrumentation of a subsystem of a CubeSat, the development team had not specified the number of thermocouples to acquire the temperature data. When questioned, they indicated that only one thermocouple should be used in the center of the plate, under the justification that other CubeSats subsystems tested in the world used that same number. This example demonstrates the lack of care and unpreparedness of the team responsible for the test parameters. A subsystem full of electronic components, fed with electrical power, that will undergo a thermal test, in the opinion of the author, should receive a more careful analysis. On the recommendation of the team responsible for the coordination of the test, in the LIT, other points were instrumented and the temperature data, during the functional tests, revealed important characteristics unknown to the developers. We emphasize that LIT is not responsible for providing or determining any data, procedure or analysis related to the test specifications for any CubeSat or subsystem to be tested. This information is the full responsibility of the project development team. However, we are concerned with performing tests that are valid and that provide relevant information, so that’s why we suggest this re-evaluation of the test instrumentation. Our recommendation, in this case, is performing a dedicated analysis of each CubeSat subsystem before any test. This analysis could provide reliable information about the critical points and demonstrate the real need for each thermocouple and its location, the need for supporting systems (radio frequency systems, power supply, among others). The example used is a further justification for the high risks that the adoption of generalist test procedures and instrumentation characteristics are not completely safe. They also show the need for a more careful bibliographical review regarding the demand for information to perform tests, avoiding any undesired surprises.

D. Test Specification We classify as test setup all the tasks related to the thermal test assembly and preparation. From the planning and assembly of temperature control, pressure, data acquisition, power cabling, the specimen positioning inside the chamber, climatic or vacuum, the specimen temperature instrumentation, and all other items required to perform the test. When the tasks refer to measures and plans related to test preparation (data acquisition, power sources, test safety procedures, interface among the chambers, specimens and systems, and others), they will be carried out by the laboratory that will perform the test. The others, as the functional test setup, must be carried out by the clients. In this case, developers should be prepared to provide all test specifications, such as specification documents and compatible power cables, for example. Figure 8 classifies the main items related to the test setup, with the responsibilities of each part (laboratory and customer) and the observations, for better understanding. It is important to emphasize that all this information should be included in a test procedure prepared by the developers, and provided to the laboratory (the main reference document for writing the internal laboratory’s test procedure). Unfortunately, a lot of this care and information is not organized or even predicted. The setting of the CubeSat positioning inside the chamber ends up being done at the time of setup. The analyses of the CubeSat interaction with the test chamber, necessary for the best use of the simulated environment, are not performed. Depending on the test chamber used, the support that the developer uses (GSE – Ground Support Equipment) for positioning the CubeSat for the test can disrupt this interaction, causing shadow and masking the test results. On more than one occasion, the coordination of the test at LIT, needed to suggest the best way to position the CubeSat inside the test facility. These suggestions and analyses take into consideration factors such as the chamber’s format, capacity and specification. These data could be requested by the developers at the time of the budget request and evaluation of the laboratory for the test. Other factors that end up causing schedule delays and demonstrate the lack of test preparation refer to not only power supply cables that are not pre-prepared and need to be assembled in a hurry by the laboratory staff but also to the lack of planning for required instruments (multimeters and oscilloscopes) and these are real and recurring examples. In this case, our analysis suggests that the detailed information regarding available test facilities and laboratory infrastructure, when requested, is important information often overlooked.

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Setup Item Laboratory Customer Observations - Temperature; - Current; Provides the systems The customer is responsible for informing Data Acquisition System - Voltage; and information which parameters need to be acquired. - Pressure; - Humidity;

The interface cabling The laboratory can provide the power Power Supply Power Supply between CubeSat and supply system but the customer is chamber responsible by request beforehand.

The location and quantity is the customer's Thermocouple - Quantity; Temperature Sensors responsibility, however the installation is the T type - Position; laboratory's responsibility.

How the CubeSat will be positioned inside CubeSat: system or Thermal Vacuum or Position inside the chamber the chamber. The laboratory will help the Subsystem Assembly Climatic Chamber customer with the CubeSat's positioning.

The laboratory provides to the customer a Contamination System Full responsible - contamination analysis as a part of its Plate security and quality norms.

- Multimeters; The laboratory can provide it, but the Support and device - - Oscilloscopes; customer is responsible by request analysis - Radio Frequency Cables; beforehand.

Figure 8. Setup items responsability.

E. Qualified Laboratories Qualified laboratories are laboratories that have their facilities, equipment and procedures qualified for integration, assembly and testing of satellites. These qualifications account for laboratories and environments with temperature control, humidity and contamination (clean rooms), equipment calibrated periodically, as established by legislation and good practices in carrying out tests, adequate documentation and procedures, support laboratories (contamination, electronics, maintenance) and use materials qualified for space application. These laboratories also have qualified personnel to perform tests, at levels of qualification and acceptance, of materials, components, subsystems and systems for space applications. They have redundant electrical power systems, composed by no-breaks and electric generators. All processes and procedures are compatible and recognized by the scientific community. As discussed previously, in Brazil, LIT is the laboratory that is qualified and specialized in the whole cycle of assembly, integration and testing of satellites and all their components and has all the necessary infrastructure for the calibration of their measurement systems as temperature, pressure, power, among others, with certification of the national and international certifying societies. Its test facilities are installed in a clean area, with controlled humidity and temperature, as determined by international standards and procedures for performing these tests. The LIT also follows strict standards for quality control of tests. With more than 25 years of experience accumulated in the participation of big satellite projects and the tools to assure the quality of the thermal tests, the authors agree that the possibility of conducting the thermal tests in CubeSats in qualified laboratories can bring some advantages to the projects. This is because the expertise of the laboratory technicians and engineers involved can also assist in the instruction of students, provide important information for testing, and provide the necessary tools and support systems.

F. Costs One of the main advantages of space programs with CubeSats is the low costs. Because they are designed and built by students of various levels of education and with components that are not 100% qualified for this application, the workforce and the components and materials have a lower cost. Research and development institutes are also 11 International Conference on Environmental Systems

taking advantage of these features to test and implement new technologies and scientific payloads. However, the small or no experience in the space product development will ultimately have inferior reliability and the use of cots components is another factor that reduces reliability since they are not designed to work in the aggressive space environment. From the point of view of costs, the launch represents the largest of them. Due to its small size and low mass, the costs related to the launch of a CubeSat are, although still high, possible to be paid. By launching them on the ride of larger satellites, the developers of the satellite launch systems were able to find a viable alternative to take advantage of a space that was underutilized. These same launchers are the ones that determine several tests that CubeSats must be submitted to. These tests are mandatory and cannot be replaced or altered, under penalty of having them rejected, and are intended to ensure that any CubeSat problems during the launch will not damage the other satellites. Because of this, the costs of these tests must be predicted by the developers. Thermal tests play important roles during the development phases of subsystems and systems. Not only mandatory but also developmental testing must be carefully planned because they can provide valuable information to developers and not just fulfillment of a requirement. It is important to emphasize that a test campaign in a laboratory has other associated costs and all these costs must be considered during the project planning phase. They are related to airline tickets, accommodation, meals, and daily costs for all involved (students, teachers and technicians) who will accompany the tests and transport costs of materials and equipment. Careful cost planning should be done to avoid cost control problems. This observation reiterates our opinion on the multidisciplinary nature of a CubeSats project, especially at a university where teachers and students in related fields, such as management and economics, could help project leaders to control costs and do some more realistic and reliable budget forecasts. Other ways to reduce costs in thermal tests, during the development of CubeSats is to perform tests known as thermo-climatic. They are only indicated for subsystems or systems in the qualification phase. These tests carried out at atmospheric pressure are usually cheaper, because they use a smaller team to control the test facility, faster transients and they do not use a large amount of nitrogen (during a thermal vacuum test, nitrogen (N2), liquid or gaseous, is used to the temperature cycling inside the chamber’s shroud). The performance of tests in thermo-climatic chambers, at atmospheric pressure, is a way to reduce costs with thermal tests for CubeSats qualification, however performing this type of test during the development of the small satellite does not exclude the need to perform a vacuum test. Because, in addition to temperature, this test also simulates another environmental condition found in orbit: low pressure.

G. The Experience That The Students Get in The Test Campaign CubeSat projects are one of the most important teaching and training tools for students in all phases of a space project. Consequently, the laboratories that will conduct the test campaign of these small satellites end up having an important position in the education of these students. In this way, LIT assumed its responsibility not only to carry out the tests, but also to assist the teachers in the student’s instruction and immersion during the whole campaign. During the CubeSat thermal tests, LIT made available its entire team of experienced and highly trained technicians and engineers. All students, teachers and technicians had the opportunity to participate in every routine of the test campaign, identical to those carried out in tests of large satellite programs. In addition to the technicians and engineers directly involved in the tests, LIT provided many other professionals from other support areas, such as data acquisition, contamination and electronics, among others. All support and training infrastructure was made available to the players and all safety standards and procedures (gloves, masks, anti-ESD protection systems) were adopted. All quality assurance procedures were adopted in carrying out thermal tests, and test procedures and reports, which guarantee and prove all the test characteristics with international validity, were performed. All this range of experience, which LIT could provide, contributes to the success of both educational and technological projects.

V. Conclusion This work presented the lessons learned by performing the qualification and acceptance tests of Brazilians CubeSat projects NANOSATC-BR1, AESP-14, SERPENS and UBATUBASAT and the Chilean CubeSat project SUCHAI. It is important to note that there were no problems during the tests performed, whether they were structural, in the laboratory, or in CubeSats, before, during, or after the tests. The main lessons learned by performing thermal tests of these projects were:

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- In several situations, the lack of knowledge of the developers, mainly project leaders, in subjects related to the tests methodology, work team management and the thermal tests preparation and organization was evident. - It is important to highlight that all projects require a dedicated thermal analysis, since there are risks in adopting any thermal test specification without previous analysis. - General procedures generally do not consider important differences as the heat distribution between 1U and 3U CubeSats, payloads, batteries, solar panels and other components. These differences may make the test performed poorly representative. - Thermal tests must be performed because they are some fundamental tools for the CubeSat project development and for increasing its reliability and not just to achieve a launcher requirement. - The instrumentation, as well as the need for thermal test systems support, must be anticipated in order to avoid delays and difficulties at the time of thermal tests. - Developers must know the test facilities that will be used to perform the thermal tests to predict and analyze the best CubeSat positioning inside the chamber to carry out the setup in order to reach the maximum interaction between the specimen and the simulated environment. - It is essential to perform thermal tests in laboratories that have chambers and equipment qualified for space devices and systems tests. - The costs for performing thermal tests, and all other tests, for the CubeSat and its subsystems qualification and acceptance, are a fundamental and important investment because they can anticipate and evidence problems that could be corrected before launch. - If there is a necessity to perform a test, whatever it is, all the information that can be obtained with it must be planned and performed. Even more when these tests are carried out on contracted infrastructures causing real financial costs related to logistics, testing, people displacement, team accommodations, etc. Mainly because a "re- test" is not an option for CubeSats projects with limited budgets. - Tests performed in climatic chambers may be interesting because they cost less than thermal tests in vacuum. Conversely, they are not valid for acceptance-level models. - The laboratory that will perform the thermal tests on CubeSats projects must be aware of its important role in the training and instruction chain of the students involved in the projects. Therefore, it should be prepared to provide to the students a favorable environment to their development. The main intention of this paper is to show to CubeSats project developers some of the problems faced during the thermal tests, at the qualification and acceptance levels. Our observations consider all the experience accumulated in conducting tests in materials, components, subsystems and systems in national and international space programs.

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