Concerning the difficult conditions under which the experiment has to work during the balloon flight, intensive testing is necessary to ensure proper data acquisition and a successful mission. Especially the low temperatures in Kiruna, which even decrease with rising altitude, are a major threat to the functionality and precision of the electronic devices included in the experiment. \change{According to \citet{ECSS_Verification}} the requirements defined in chapter \ref{sec:experiment_requirements_and_constraints} can be verified by the following four verification methods:
Since most of the electronic devices are standard at the Department of Extraterrestrial Physics, they can be verified by review-of-design \replaced{or}{and} analysis \replaced{including}{or} similarity. The planned tests and their results are documented here as part of the experiments verification. In section \ref{sec:verification_matrix}, the verification process of the different requirements is briefly explained. In addition, a table of the different requirements, their verification type as well as their verification status are given. In section \ref{sec:verification_plan} all tests are presented in detail, including test facility and procedure. Section \ref{sec:verification_results} contains the test results. \change{Only the major tests will be described in this chapter. Documenting every minor subsystem test in the \ac{SED} would take more time than the actual test.}
\ftwoone&\ftwoonet&\tfive, \tsix, \teight& Can be verified by starting the instrument on ground. &\tfive\Done, \tsix\Done, \teight\Done&\cellcolor{Verified}Verified \\
\ftwotwo&\ftwotwot&\tfive, \tsix, \teight& Can be verified by starting the instrument on ground. &\tfive\Done, \tsix\Done, \teight\Done&\cellcolor{Verified}Verified \\
\fthree&\fthreet& R, I, S, \change[3]{\tsix}& Can be verified by reviewing the instrument design and assuring conformance to the design by inspection as well as assuring similarity to previous \ac{BEXUS} missions from Kiel University. \change[3]{Can also be verified by test measurements on ground.}& R\Done, I\Done, S\Done, \change[3]{\tsix\Done}&\cellcolor{Verified}Verified \\
\poneone&\poneonet& S & Can be verified by comparing the instrument to previous \ac{BEXUS} instruments from Kiel University \change[3]{and performing an analysis to calculate the maximum number of particle interactions which can be recorded.}& S\Done, \change[3]{\afour\Done}&\cellcolor{Verified}Verified \\
\ponetwo&\ponetwot& R, \change[3]{\tsix}& Can be verified by reviewing the design of the Cherenkov detector \change[3]{and performing test measurements}. & R\Done, \change[3]{\tsix\Done}&\cellcolor{Verified}Verified \\
\ptwoone&\ptwoonet& R, \change[3]{\tsix}& Can be verified by reviewing the data sheet and performing functionality tests. & R\Done, \change[3]{\tsix\Done}&\cellcolor{Verified}Verified \\
\ptwotwo&\ptwotwot& R, \change[3]{\tsix}& Can be verified by reviewing the data sheet and performing functionality tests. & R\Done, \change[3]{\tsix\Done}&\cellcolor{Verified}Verified \\
\ptwothree&\ptwothreet& R, \change[3]{\tsix}& Can be verified by reviewing the data sheet. & R\Done, \change[3]{\tsix\Done}&\cellcolor{Verified}Verified \\
\ptwofour&\ptwofourt& R, \change[3]{\tsix}& Can be verified by reviewing the data sheet and performing functionality tests. & R\Done, \change[3]{\tsix\Done}&\cellcolor{Verified}Verified \\
\ptwofive&\ptwofivet& I, \change[3]{\tsix}&\change[3]{Can be verified by inspecting the software code and performing functionality tests.}& I\Done, \change[3]{\tsix\Done}&\cellcolor{Verified}Verified \\
\ptwosix&\ptwosixt& I, \change[3]{\tsix}&\change[3]{Can be verified by inspecting the software code and performing functionality tests.}& I\Done, \change[3]{\tsix\Done}&\cellcolor{Verified}Verified \\
\dthreetwo&\dthreetwot& I, R &\change[3]{Can be verified by reviewing the instrument design and inspecting the instrument to assure conformance to the design.} The design was developed using the expertise from the Department of Extraterrestrial Physics and is considered to be sufficient. A shock test will therefore not be performed to avoid unnecessary stress to the sensitive detectors. & I\Done, R\Done&\cellcolor{Verified}Verified \\
\dthreethree&\dthreethreet&\afive, \tnine& Can be verified by performing an analysis of the stress applied to the screws of the mechanical interface and and a static load test of the mounting rails. &\afive\Done, \tnine\Done&\cellcolor{Verified}Verified \\
\dfourone&\dfouronet& I, R & Can be verified by reviewing the instrument design and inspecting the instrument to assure conformance to the design. & I\Done, R\Done&\cellcolor{Verified}Verified \\
\dfourtwo&\dfourtwot& I, R & Can be verified by reviewing the instrument design and inspecting the instrument to assure conformance to the design. & I\Done, R\Done&\cellcolor{Verified}Verified \\
\dfourthree&\dfourthreet& I, R & Can be verified by reviewing the instrument design and inspecting the instrument to assure conformance to the design. & I\Done, R\Done&\cellcolor{Verified}Verified \\
\dfiveone&\dfiveonet&\aone, \tfive, \teight& Can be verified by thermal calculations and thermal vacuum tests. &\aone\Done,\tfive\Done, \teight\Done&\cellcolor{Verified}Verified \\
\dfivetwo&\dfivetwot&\tone, \ttwo, \tfive, \teight& Can be verified by tests of the pressure housing and thermal vacuum tests. &\tone\Done, \ttwo\Done, \tfive\Done, \teight\Done&\cellcolor{Verified}Verified \\
\dfivethree&\dfivethreet& I, R, \tfive, \teight& Can be verified by reviewing the instrument design and assuring conformance to the design by inspection as well as thermal vacuum tests. & I\Done, R\Done, \tfive\Done, \teight\Done&\cellcolor{Verified}Verified \\
\dsixone&\dsixonet& I, R & Can be verified by reviewing the instrument design and assuring conformance to the design by inspection. & I\Done, R\Done&\cellcolor{Verified}Verified \\
\dsixtwo&\dsixtwot&\tseven, R, \atwo& Can be verified by a combination of review-of-design and estimations of the power consumption as well as a power supply test. &\tseven\Done, R\Done, \atwo\Done&\cellcolor{Verified}Verified \\
\dsevenone&\dsevenonet& I, R & Can be verified by reviewing the instrument design and assuring conformance to the design by inspection. & I\Done, R\Done&\cellcolor{Verified}Verified \\
\dseventwo&\dseventwot&\athree& Can be verified by calculating the data rate from the expected particle flux. &\athree\Done&\cellcolor{Verified}Verified \\
\dseventhree&\dseventhreet& I, R & Can be verified by reviewing the instrument design and assuring conformance to the design by inspection. & I\Done, R\Done&\cellcolor{Verified}Verified \\
\dsevenfour&\dsevenfourt& I, R & Can be verified by reviewing the instrument design and assuring conformance to the design by inspection. \change[4]{Furthermore, an analysis can be performed.}& I\Done, R\Done, \change[4]{\asix\Done}&\cellcolor{Verified}Verified \\
\oone&\oonet& I, R & Can be verified by reviewing the instrument design and assuring conformance to the design by inspection. & I\Done, R\Done&\cellcolor{Verified}Verified \\
\otwo&\otwot& I, R & Can be verified by reviewing the instrument design and assuring conformance to the design by inspection. & I\Done, R\Done&\cellcolor{Verified}Verified \\
\othree&\othreet& I, R & Can be verified by reviewing the instrument design and assuring conformance to the design by inspection. & I\Done, R\Done&\cellcolor{Verified}Verified \\
\ofour&\ofourt& I, R & Can be verified by reviewing the instrument design and assuring conformance to the design by inspection. & I\Done, R\Done&\cellcolor{Verified}Verified \\
\ofive&\ofivet& I, R & Can be verified by reviewing the instrument design and assuring conformance to the design by inspection. & I\Done, R\Done&\cellcolor{Verified}Verified \\
% \item \fone, \foneone\:and \fonetwo\:can be verified by measuring muons on ground.
% \item \ftwoone\:and \ftwotwo\: can be verified by starting the instrument on ground, for example during the thermal vacuum tests.
% \item \fthreeone\:to \fthreesix\:can be verified by comparing the \ac{CHAOS} instrument to previous instruments from the Department of Extraterrestrial Physics which used the electronical components and software before. Furthermore, these requirements can be verified by starting the instrument on ground.
% \item \pone\:can be verified by comparing the \ac{CHAOS} instrument to similar instruments from the Department of Extraterrestrial Physics and the flight data acquired by these instruments.
% \item \ptwoone\:and \ptwotwo\:can be verified by a thermal vacuum test.
% \item \pthreeone\:and \pthreetwo\:can be verified by comparing the \ac{CHAOS} instrument to previous instruments from the Department of Extraterrestrial Physics which used the electronical components and software before. Furthermore, these requirements can be verified by starting the instrument on ground.
% \item \pthree\:can be verified by comparing the \ac{CHAOS} instrument to previous instruments from the Department of Extraterrestrial Physics which used the electronical components and software before. Furthermore, this requirement can be verified by starting the instrument on ground.
% \item \done\:and \dtwo\:can be verified by weighing the instrument and measuring its dimensions.
% \item \dthree\:can be verified by a vibration test.
% \item \dfourone\:can be verified by inspection and review-of-design. By looking at the design documents and by inspecting the instrument it can be made sure that people working with the instrument will not be exposed to the high voltage.
% \item \dfourtwo\:can be verified by starting the instrument on ground. A vacuum test can verify that the pressure housing works.
% \item \dfiveone\:to \dfivethree\:can be verified by a thermal vacuum test.
% \item \dsixone\:can be verified by inspection and review-of-design. By inspecting the instrument and reviewing the design documents the compatibility with the gondola battery can be ensured. Furthermore, this requirement can be tested by connecting the instrument to a power source similar to the \ac{BEXUS} battery.
% \item \dsixtwo\:can be verified by a power calculation.
% \item \dsevenone\:to \dsevenfour\:can be verified by review-of-design through looking at the software and corresponding documentation.
% \item \deight\:can be verified by a calculation of expected particle events.
\replaced{This section provides the verification plan. There will be no exact dates scheduled for the verifications done by inspection, analysis including similarity and review-of-design because they are not as time consuming as the tests. They will instead be done throughout the project.\\The tests planned are described below.}{This section provides information about the tests for verification.}
Procedure & The pressure housing consisting of the aluminum base plate and die-cast aluminum box is inflated with air. The pressure difference between the inside and outside of the housing will be steadily increased to values larger than 1\,bar. This test determines whether or not the design of the pressure housing has to be adjusted. During the \ac{BEXUS} flight pressure differences larger than 1\,bar are physically not possible.\\\hline
Procedure & The pressure housing consisting of the aluminum base plate and die-cast aluminum box is strengthened by additional U-profiles and placed in a vacuum chamber. Now the chamber is evacuated creating a pressure difference of approximately 1\,bar between the inside and outside of the housing. The leakage rate is recorded over the course of four days. During the \ac{BEXUS} flight pressure differences larger than 1\;bar are physically not possible. \\\hline
Procedure & The experiment will be \change[3]{tested for functionality while being} exposed to sufficient vibration \replaced{and tested for functionality afterwards.}{for ten minutes.}\deleted[3]{\change{The transport to the \ac{EAR} will serve as vibration source.}}\change[4]{To achieve the necessary vibration, the experiment will be placed on a cart and pushed over an obstacle course.}\\\hline
Test campaign duration &\replaced[4]{One day}{\replaced[3]{\acs{TBD}}{\replaced{Duration of the transportation to the \ac{EAR}}{Ten minutes}}}\\\hline
Test campaign date &\replaced[4]{21st August 2024}{August/September 2024}\\\hline
Procedure & The instrument \replaced{without}{including} the insulation is tested in a thermal vacuum chamber under similar pressure and temperature conditions as during the \ac{BEXUS} flight. \replaced{Several temperature and pressure measurements will be performed.}{Several temperature sensors and pressure sensors will measure the temperature on the sensor head, the power board and the experiments rails and the pressure inside of our box.} Additionally, it will be tested if \replaced{the \acf{HV} and data storage turn off}{the instrument turns itself off} when the pressure rises above 800\,mbar. \\\hline
Procedure & The experiment will be connected to an external \replaced[3]{power source during multiple test measurements.}{battery source similar to the one during the \ac{BEXUS} flight}. It will be checked whether the power supply was sufficient \change[3]{and all components worked as expected. The total power consumption will be determined.}\\\hline
Procedure & The instrument including the insulation is tested in a thermal vacuum chamber under similar pressure and temperature conditions as during the \ac{BEXUS} flight. \replaced{Several temperature and pressure measurements will be performed.}{Several temperature sensors and pressure sensors will measure the temperature on the sensor head, the power board and the experiments rails and the pressure inside of our box.} Additionally, it will be tested if the instrument turns itself off when the pressure rises above 800\,mbar. \\\hline
Test facility &\acs{IEAP}, \acs{CAU} Kiel \\\hline
Tested item & Mounting rails and interface plate. \\\hline
Model & Protoflight \\\hline
Procedure & The mounting rails are placed on two wooden beams creating a setup similar to the experiment mounting to the gondola. The interface plate of the experiment is placed on the rails and stressed with the needed weight to achieve the required static load. Afterwards, the rails are inspected for permanent deformations.\\\hline
A more detailed description of the presented thermal calculations can be found on the \ac{RX/BX} team site under \url{https://rexusbexus.zarm.uni-bremen.de/share/page/} in the folder \texttt{CHAOS/Verification/}.
Verification description & The \ac{CHAOS} instrument is planned to use a styrofoam box for thermal control similar to previous \ac{BEXUS} missions from Kiel University. To show that the experiment will stay within the desired temperature range, the model is applied to a set of different boundary conditions and real temperature measurements from the BX19 flight.\\\hline
Results & The application of the model to the outside temperatures for the BX19 flight provided by the \ac{RX/BX} organizers leads to results which are consistent with the thermal behaviour of the \ac{ADAM} experiment. \ac{ADAM} was part of BX19. The standard parameters were used.
Combinations of typical boundary conditions were tested using the standard parameters, leading to temperatures of the pressure housing which are still in the survivable range after four hours. The equilibrium temperature was not reached after four hours.
The thermal behaviour during the flight depends on the instrument temperature during the launch. The heating on the launch pad can be influenced by the time the instrument is activated prior to launch.
The experiment can only get too hot prior to launch. After the launch the experiment will only get colder up until the landing.
Because of the limitations of the used model, a proper thermal balance test needs to be carried out to gain a better understanding of the thermal behaviour of the experiment.\\\hline
The pressure housing is represented by a homogeneous, volume heated, thin plate with surface $A_\text{p}$ and a constant heating power of $P_\text{heat}\approx4.1\,\mathrm{W}$. This is the heat dissipated by the electronics inside the pressure housing. The heat is transferred to the styrofoam insulation via radiation which is also modelled as a plate. Convection is neglected because of the low air pressure expected during the \ac{BEXUS} flight. Lastly, the heat is transferred through the styrofoam to the outside via thermal conduction. All physical quantities of the pressure housing and styrofoam like thermal conductivity are considered to be independent of time and temperature. The temperature of the pressure housing is called $T_\text{p}$, the temperature of the inside wall of the styrofoam $T_\text{i}$ and the temperature of the outside wall $T_\text{o}$.
\caption{Thermal model of the \ac{CHAOS} instrument.}
\label{fig:setup_thermal}
\end{figure}
The model takes initial values for $T_\text{p}$ and $T_\text{i}$ and is applied to a time series of values for $T_\text{o}$. For each time step new values $T^\prime_\text{p}$ and $T^\prime_\text{i}$ are calculated based on $T_\text{p}$, $T_\text{i}$ and the outside temperature $T_\text{o}$.
The heat difference $\Delta Q_\text{p}$ of the pressure housing in each time step can be calculated by multiplying the difference of the heating and cooling power with the time resolution $\Delta t$. While the cooling power $P_\text{cool}$, which models the radiation from the pressure housing to the styrofoam box, is described by the Stefan-Boltzmann law taking the reflection between the two walls into account), the heating power is assumed to be constant with $P_\text{heat}=4.1\,\mathrm{W}$:
For the area $A_\text{sty}$ of the styrofoam insulation the mean of the inside and outside area is used. Using these equations and the specific heat capacities $c_\text{w}$ and masses $m$ of the aluminum pressure housing and styrofoam insulation the temperatures of the next time step can be calculated:
The model was implemented in \texttt{python} and can be found on the \ac{RX/BX} team site under \url{https://rexusbexus.zarm.uni-bremen.de/share/page/} in the folder \texttt{CHAOS/Verification/}. Varying the model parameters within a sensible range let to a set of standard parameters for the given formulas which can be taken from the source code. It has to be kept in mind that these are often only approximations or guessed. For example, the mean of the inside and outside area of the styrofoam box was taken to find an area for the styrofoam insulation which is used in the calculations. Two parameters were hard to estimate and shall be highlighted. The first parameter is the total mass of all aluminum parts of the pressure housing and the second parameter is the emissivity of the pressure housing because of its powder coating. The chosen standard parameters are $m_\text{p}=7.0\,\mathrm{kg}$ and $\epsilon_\text{p}=0.6$.
\subfigure[Temperature and pressure measurements of the \ac{ADAM} experiment (BX19) which had a heating power of $P_\text{heat}=6.5\,\mathrm{W}$.]{\includegraphics[width=0.59\textwidth]{images/verification/thermal_adam.png}\label{fig:verification_thermal_adam}}
\subfigure[Thermal model applied to the outside temperature of the BX19 flight using the standard parameters.]{\includegraphics[width=0.39\textwidth]{images/verification/chaos_thermal_adam_bx19.pdf}\label{fig:verification_thermal_chaos_adam}}
\caption{Thermal properties of BX19.}
\end{figure}
The ambient pressure and the thermal behaviour of the \ac{ADAM} experiments during its flight can be seen in figure \ref{fig:verification_thermal_adam}. It is important to note that the experiment was heated to a temperature of almost $\un{35}{^\circ C}$ before launch. In figure \ref{fig:verification_thermal_chaos_adam} the thermal model was applied to the outside temperature of the BX19 flight, which was the \ac{ADAM} flight. Similar to the \ac{ADAM} experiment, starting temperatures of $T_\text{p0,i0}=\un{35}{^\circ C}$ were used. The model gives a temperature at the end of the flight which is around $\un{10}{^\circ C}$ colder than the \ac{ADAM} experiment.
\begin{figure}[h]
\centering
\subfigure[Example application of the thermal model.]{\includegraphics[width=0.49\linewidth]{images/verification/example_idealized_temperature.pdf}\label{fig:verification:example_application}}
\subfigure[Thermal model applied to different boundary conditions using the standard parameters.]{\includegraphics[width=0.49\linewidth]{images/verification/boundary_conditions_standard_parameters.pdf}
\label{fig:verification:boundary_conditions}}
\caption{Application of the thermal model.}
\end{figure}
The thermal model was applied to a set of typical boundary conditions for \ac{BEXUS} flights. To evaluate the calculated temperature $T_\text{p}$ of the pressure housing an exponential function $T(t)$ was fitted to the results giving a time constant $\tau$ and equilibrium temperature $T_\text{p,eq}$ to characterize the thermal behaviour:
An example of such a fit can be seen in figure \ref{fig:verification:example_application}. The results for different boundary conditions are presented in figure \ref{fig:verification:boundary_conditions}.
Figure \ref{fig:boundary_conditions_extreme_cases_4W} shows the temperature $T_\text{p}$ of the pressure housing for the extreme cases of the boundary conditions. \change[3]{The boundary conditions were chosen based on data from previous \acs{BEXUS} flights and the pre-flight heating of the \acs{ADAM} experiment. The lower survivable temperature is determined by the datasheet of the photodiodes. The real lower boundary is most likely even lower. Temperature calibrations with these diodes were done at the Department for Extraterrestrial Physics for temperatures below $\un{-50}{^\circ\mathrm{C}}$.} The temperature stays within the surviving temperature range for at least four hours. The temperature ranges are based on the information in section \ref{sec:thermal_design}.
\change[3]{Adjustments to the electronics (see section \ref{sec:power}) lead to a higher power consumption of 5.0\,W which is higher than the estimated 4.1\,W. The calculations were therefore also performed with a heating power of 9\,W as extreme case. With this heating power the instrument stays in the survivable range for a total of six hours as can be seen in figure \ref{fig:verification:boundary_conditions_extreme_cases_9W}. Therefore, no heater will be implemented.}
Results & The instrument draws a current of 178\,mA at a voltage of 28\,V if all systems are running. This leads to a power consumption of approximately 5.0\,W, which is larger than the estimated power consumption of 4.1\,W due to the addition of a linear regulator to the power board during the integration of the instrument. If the battery provides 360\,Wh, the experiment can run for around 72 hours. The balloon flight itself will only last for several hours. Even a higher power consumption is possible. With 9\,W the instrument will be able to run for 40 hours.\\\hline
Results & Every particle event generates a downstream of 96 bytes = 768 bits. Based on previous \ac{BEXUS} missions from Kiel University a particle count rate of \replaced[3]{200}{100}\,counts/s is assumed. This multiplies to a downlink rate of \replaced[3]{approximately 154}{less than 100} kbit/s.\\\hline
Conclusions & Requirement \dseventwo\:is met. If larger particle count rates should appear during the \ac{BEXUS} flight, the trigger thresholds can be adjusted. Furthermore, the downlink rate is limited to 200\,kbit/s in the program code.\\\hline
% Pierre soll mal ausrechnen, was das IRENA an max. Events pro Sekunde schafft. Bei CHAOSjunior hatten wir counts bis 60 pro s, wenn nur ein Detektor getriggert werden musste... Wir können die Downlink-Rate über die Frequenz der Pakete setzen: packetsize/packetfreq $= \frac{\SI{512}{byte}}{\SI{0.02}{s}}\approx\SI{25}{Kbyte/s}\approx\SI{200}{kbit/s}$, $\frac{\SI{200}{kbit/s}}{\SI{96}{byte/particle}\mathrm{(von \ Ava)}}=\SI{260}{particle/s}$.
Verification description & The maximum number of particle interactions which can be recorded is calculated.\\\hline
Results & A maximum downlink rate of 200\,kbit/s is assumed. Every particle event leads to a downstream of 96\,bytes = 768\,bits. This leads to a maximum of 260 particle events which can be recorded per second.\\\hline
Verification description & Both the connection of the experiment to the mounting rails and the connection of the mounting rails to the gondola is achieved by using 4\:M6\:screws. The force applied to the M6 screws under the static load requirements is calculated and compared to the tensile strength of the screws.\\\hline
Results & With an assumed mass of 14\:kg, which has a large safety margin compared to the current mass estimation, the experiment has to be stressed with 140\,kg to meet the static load requirement of an applied load of 10 times the experiment's mass in vertical direction. This force of $F\approx140\,\text{kg}\cdot10\,\frac{\text{m}}{\text{s}^2}=1400\,\text{N}$ is distributed between the four screws leading to a stress of 350\,N per screw. The stress cross-section of a M6 screw is 20.1 mm$^2$ (\url{https://de.wikipedia.org/wiki/Metrisches_ISO-Gewinde}). Each screw is therefore stressed with $\sigma=\frac{F}{A}=\frac{350\,\text{N}}{20.1\,\text{mm}^2}\approx17.4\,\text{MPa}$. For stainless steel the yield tensile strength is 215\,MPa (\url{https://matweb.com/search/DataSheet.aspx?MatGUID=abc4415b0f8b490387e3c922237098da&ckck=1}) which leads to a sufficiently large safety factor. With such a large safety factor it can be assumed that the screws will also hold an acceleration of 5g from the side. \\\hline
Verification description & The data rate of the uplink is calculated from the specs of the \ac{IRENA} board and its software.\\\hline
Results & The \ac{IRENA} can process commands with a maximum length of 128 characters. Each character has 8 bits leading to a maximum size of 1024 bits per command. This means four commands with the maximum can be send per second and the data rate is still below 4.8 kbit/s. The KeepAlive() function of our ground stations pings the experiment every 30 seconds and sends one command. Every other command is sent by hand. \\\hline
A more detailed description of test \tone\:can be found on the \ac{RX/BX} team site under \url{https://rexusbexus.zarm.uni-bremen.de/share/page/} in the folder \texttt{CHAOS/Verification/}.
Verification description & The pressure housing shall ensure atmospheric pressure for the experiment during the flight to mitigate the risk of corona discharges caused by the \ac{HV}. Therefore, the pressure housing was inflated using a tire inflator. The pressure difference was steadily increased to differences larger than $\un{1}{bar}$. Different designs of the pressure housing were tested.\\\hline
Expected results & The pressure housing starts to loose air for pressure differences smaller than $\un{1}{bar}$ because the aluminum base plate bends. Additional U-profiles pressing the die-cast aluminum box onto the base plate make pressure differences larger than $\un{1}{bar}$ possible. \\\hline
Obtained results & Without additional reinforcements of the pressure housing the base plate deforms in a way that the housing starts to leak at an additional pressure of $\un{0.3}{bar}$.
With a single additional U-profile pressing the aluminum box onto the base plate the pressure housing stays airtight at an additional pressure of $\un{1.2}{bar}$. The leakage rate was determined to be $Q=\frac{pV}{\Delta t}=(-0.020\pm0.005)\,\frac{\mathrm{mbar}\cdot\mathrm{l}}{\mathrm{s}}$.
With two additional U-profiles the pressure housing holds an additional pressure of $\un{1.0}{bar}$. No leakage was detectable with the chosen test setup using a tire inflator. \\
\hline
Conclusions & The setup with two U-profiles ensures an airtight pressure housing and will be the setup used from this point onwards.\\\hline
\subfigure[Pressure housing with additional U-profiles.]{\includegraphics[width=0.49\linewidth]{images/verification/total_view.jpg}\label{fig:verification:total_view}}
\subfigure[Test setup with tire inflator.]{\includegraphics[width=0.49\linewidth]{images/verification/manometer.jpg}
A more detailed description of test \ttwo\:can be found on the \ac{RX/BX} team site under \url{https://rexusbexus.zarm.uni-bremen.de/share/page/} in the folder \texttt{CHAOS/Verification/}.
Verification description & The pressure housing shall ensure atmospheric pressure for the experiment during the flight to mitigate the risk of corona discharges caused by the \ac{HV}. A pressure and temperature sensor was placed inside the pressure housing. For the pressure housing the setup with two additional U-profiles was used. The pressure housing was placed inside a thermal vacuum chamber which was evacuated to pressures around $\un{10^{-1}}{mbar}$ for a total of four days. \\\hline
Expected results & The pressure housing is airtight and has a leakage rate which is negligible in the context of the \ac{BEXUS} flight environments. Furthermore, the base plate shows no plastic deformations after the test.\\\hline
Obtained results & The vacuum test with the setup which uses two additional U-profiles leads to a leakage rate of $Q=\frac{pV}{\Delta t}=(-3.0162\pm0.0014)\cdot10^{-3}\,\frac{\mathrm{mbar}\cdot\mathrm{l}}{\mathrm{s}}$.
The vacuum test under flight conditions lead to no plastic deformation of the base plate. This means a pressure loss because of a breaking base plate is very unlikely.
Over the course of four days approximately $\un{100}{mbar}$ leaked out of the pressure housing.\\\hline
Test type & Verification of Mass and Volume\\\hline
Test facility &\ac{IEAP}, \ac{CAU} Kiel\\\hline
Verified item & Whole instrument \\\hline
Verification description & The whole experiment was placed on a scale to measure its weight. Some screws were placed on top of the experiment to compensate the missing screws for the connection to the gondola. A tape measure was used to measure the experiments dimensions. \\\hline
Expected results & A mass of 12.63\,kg was expected. The expected dimensions of the experiment were $495\,\text{mm}\times395\,\text{mm}\times370\,\text{mm}$ without rails and $600\,\text{mm}\times395\,\text{mm}\times381\,\text{mm}$ with rails.\\\hline
Obtained results & The experiment's mass was determined to be 11.9\,kg as can be seen in figure \ref{fig:verification:mass}. Furthermore, the experiment's dimensions are $495\,\text{mm}\times393\,\text{mm}\times367\,\text{mm}$ without rails and $600\,\text{mm}\times393\,\text{mm}\times374\,\text{mm}$ with rails. \\\hline
Conclusions & Requirements \done\:and \dtwo\:are met and the experiment fits on to the gondola.\\\hline
Verification description &\ac{CHAOS} was placed on a cart together with the laptop to record the measured data (see figure \ref{fig:verification:cart}). The whole setup was then pushed across an obstacle course (see figure \ref{fig:verification:course}) twice and the instrument was checked for functionality during the test and afterwards. \\\hline
Expected results & The instrument works as expected and no screws become loose. The vibrations while crossing the obstacle course will be visible in the counts of the different detectors. \\\hline
Obtained results & A visual inspection showed that no screws became loose. Figure \ref{fig:verification:chaos_vibration} shows the housekeeping data recorded during the vibration test. The instrument recorded all relevant data throughout and after the test. Interesting are the counts of events detected by the different detectors shown in the bottom three panels. These count rates are binned in intervals of ten seconds. The two peaks correspond to the heavy vibrations due to the impacts on the obstacles during the two crossings of the course. It can be seen that the count rates normalize after the vibrations occurred. \\\hline
Conclusions & The instrument keeps working while being exposed to vibrations. Requirement \dthreeone\:is met. The vibrations can be seen as increased counts in the different detectors and are due to the impact on the obstacles. If strong and sudden vibrations occur during the flight (e.g. when the balloon is cut), they will be visible in the recorded data. This problem can be solved by filtering techniques already successfully applied on data from \ac{CHAOS}junior. \\\hline
\end{longtable}
\begin{figure}[H]
\centering
\subfigure[\ac{CHAOS} on the cart.]{\includegraphics[width=0.49\linewidth]{images/verification/cart.jpg}\label{fig:verification:cart}}
Verification description & The whole experiment without its insulation was placed inside the thermal vacuum chamber for two separate runs and tested under flight conditions (see figure \ref{fig:verification:chaos_tvac_aug}). The backing pump was used to evacuate the chamber to a pressure below $10^{-1}$\,mbar. To thermally couple the base plate of the instrument to the cold plate of the chamber, a heat conductive material was used (see figure \ref{fig:verification:heat_conducting_material}). The cold plate of the thermal vacuum chamber was set to different temperatures which are expected during the flight according to analysis \aone. Once a thermal equilibrium was reached for each temperature, a leakage rate could be calculated. Furthermore, the automatic stoppage of data storage and shutdown of the \ac{HV} during descent was tested. As a safety measure against condensation, the instrument was purged with N$_2$ before the second run.\\\hline
Expected results & The pressure housing keeps the atmospheric pressure under flight conditions and the automatic stoppage of data storage and shutdown of the \ac{HV} during descent works as expected. Furthermore, the experiment should keep working in the temperature environments expected during the flight.\\\hline
Obtained results & The automatic stoppage of the data storage and shutdown of the \ac{HV} worked partially. The instrument was not able to detect the end of the ascending phase and had to be set into floating mode by hand. Nevertheless, the detection of pressures above 800\,mbar during the venting of the chamber worked. The instrument kept working in the tested temperature environments. The external pressure sensor worked, but some data was lost due to a loose contact within a harness used inside the thermal vacuum chamber. It is important to stress that the error was not caused by the \ac{CHAOS} instrument. \\\hline
Conclusions & The pressure housing holds atmospheric pressure under flight conditions and fulfills requirement \dnine. A software fix was performed to let the instrument detect the beginning oof the floating phase. This fix will be tested during \teight\:at \ac{ZARM}. Risks TC02-1 and TC02-2 can be lowered.\\\hline
\end{longtable}
\begin{figure}[H]
\centering
\subfigure[Heat conducting material on the bottom of the base plate.]{\includegraphics[width=0.49\linewidth]{images/verification/thermal_conducting_medium.jpg}\label{fig:verification:heat_conducting_material}}
\subfigure[Pressure housing inside the thermal vacuum chamber.]{\includegraphics[width=0.49\linewidth]{images/verification/chaos_tvac_chamber_aug.jpg}
Figures \ref{fig:verification:leakage_rate_chaos_aug1} and \ref{fig:verification:leakage_rate_chaos_aug2} show the temperature and pressure recorded by the pressure sensor inside the pressure housing of \ac{CHAOS}. The sensor is placed on the \ac{FPGA} which is the hottest part of the electronics. Table \ref{tab:verification:leakage_aug} lists the temperatures to which the thermal vacuum chamber was set, the internal equilibrium temperatures inside the pressure housing and the leakage rates calculated from the recorded pressures. It can be seen that the absolute values of the leakage rate are two magnitudes below $0.3\,\frac{\mathrm{mbar}\cdot\mathrm{l}}{\mathrm{s}}$. Therefore, requirement \dnine is met.\\
\textbf{Chamber temperature in $^\circ$C}&\textbf{Internal temperature in $^\circ$C}&\textbf{Leakage rate in $\frac{\mathrm{mbar}\cdot\mathrm{l}}{\mathrm{s}}$}\\
\subfigure[First run of thermal vacuum test \tfive.]{\includegraphics[width=0.49\linewidth]{images/verification/leakage_rate_chaos_aug1.pdf}\label{fig:verification:leakage_rate_chaos_aug1}}
\subfigure[Second run of thermal vacuum test \tfive.]{\includegraphics[width=0.49\linewidth]{images/verification/leakage_rate_chaos_aug2.pdf}
\label{fig:verification:leakage_rate_chaos_aug2}}
\caption{\change[4]{Results of thermal vacuum test \tfive.}}
Verification description & The whole experiment was turned on and off in during the integration of the instrument to ensure proper functionality of the different detector stages. \\\hline
Expected results & The \ac{CHAOS} instrument is able to detect muons from \acp{GCR} during measurements on ground. While \ac{BGO} scintillation crystal and the \acp{SSD} measure signals corresponding on the energy losses of the muons passing through them, the Cherenkov detector detects light for muons with energies above approximately 200\,MeV. \\\hline
Obtained results & The \acp{SSD} and \ac{BGO} scintillator can measure the energy losses and the Cherenkov detector sees the expected Cherenkov light. For some detectors the noise has to be handled.\\\hline
Conclusions & The detectors are able to perform the required measurements.\\\hline
Obtained results & The instrument draws around 151\,mA at 28\,V leading to a power consumption of around 4.2\,W without the added linear regulator on the power board (see section \ref{sec:power}). With the regulator 178\,mA are drawn leading to a power consumption of 5.0\,W. \\\hline
Verification description & The whole instrument including the insulation was placed inside the TVAC chamber on mounting rails similar to those on the \ac{BEXUS} gondola. In addition to the instrument's own temperature and pressure sensors, temperature sensors provided by \ac{ZARM} were placed on the outside of the pressure housing, the inside and outside of the insulation box as well as the gondola rails. For the test, the temperature and pressure environments expected during flight were simulated. First, the chamber was evacuated to a pressure around 10\,mbar. Afterwards, the chamber was cooled down to -50\,$^\circ$C. The instrument stayed at these conditions for around half an hour, before the chamber was heated to ambient temperature and then vented. Prior to evacuating the chamber, a voltage margin test was performed with possible input voltages which can occur during flight. It cannot be guaranteed that the battery always provides +28\,V. Steps of 2\,V between +28\,V and +38\,V were used with the exact values being listed in table \ref{tab:voltage_margin_test}.\\\hline
Expected results & The pressure housing stays airtight and no unusual leakage occurs. Furthermore, the automatic \ac{HV} shutdown and stop of data writing to the SD card during the venting work as expected. The instrument stays functional under the expected temperature and pressure conditions during flight. Lastly, the instrument behaves according to the thermal model from analysis \aone. Furthermore, the instrument works at the different input voltages.\\\hline
Obtained results & The pressure housing remained airtight. Both the \ac{HV} shutdown and stoppage of data writing worked. The instrument kept its functionality under the tested temperature and pressure conditions with the observed thermal behaviour being in compliance with the thermal model from analysis \aone. Lastly, the instrument could handle the different input voltages.\\\hline
Conclusions & The last pending requirements were met and the instrument was accepted for the launch campaign. \ac{CHAOS} remained at \ac{ZARM} in Bremen for transportation to \acs{Esrange} Space Center. \\\hline
\caption{Thermal model from analysis \aone~applied to test \teight. The numbers 3, 4 and 5 correspond to the phases of the tests in which the chamber pressure was around 10\,mbar.}
\label{fig:verification:zarm_thermal_model}
\end{figure}
Figure \ref{fig:verification:chaos_zarm} shows \ac{CHAOS} inside the TVAC chamber. The housekeeping data from test \teight~can be seen in figure \ref{fig:verification:zarm_hk}. \ac{ZARM} provided additional pressure sensors which were placed at the nodes from the thermal model from analysis \aone. The model was applied to the measured temperatures as shown in figure \ref{fig:verification:zarm_thermal_model}. The input temperature was the outside temperature of the polystyrene insulation. Both calculated temperatures for the inside of the insulation and the pressure housing comply with the measured values. The largest absolute deviation of 8\,$^\circ$C is still smaller than the possible deviation in the input temperature which can be expected during flight depending on the weather.
Verified item & Mounting rails and interface plate \\\hline
Verification description & The mounting rails were placed on two wooden beams creating a setup similar to the experiment mounting to the gondola. The interface plate of the experiment was placed on the rails together with the cover of the styrofoam box and stressed with a static load of 131.1\,kg (see figure \ref{fig:verification:weight}). This is more than the required 10 times of the experiment's weight based on the most recent mass estimation of 12.63\,kg at the time of the test.\\\hline
Expected results & The rails should show elastic deformation while the static load is applied. No permanent deformation of the rails should occur. \\\hline
Obtained results & The rails show elastic deformation while the static load is applied, but no permanent deformation of the rails was detected. \\\hline
\subfigure[Static load applied to the rails.]{\includegraphics[width=0.35\linewidth]{images/verification/weight.jpeg}\label{fig:verification:weight}}
\subfigure[Deformation of the rails under the application of the static load.]{\includegraphics[width=0.624\linewidth]{images/verification/stressed.jpeg}
\label{fig:verification:stressed}}
\subfigure[Mounting rails after the static load test.]{\includegraphics[width=0.55\linewidth]{images/verification/no_deformation.jpeg}}
