Nano-Stratospheric Aerosol Measurement (NanoSAM) Conceptual . - Colorado

2.3.Concept of OperationsThe general concept of operations (CONOPS) for the NanoSAM CubeSat project proposed by Ball Aerospace includesthe design, construction, launch and operation of a solar occultation data acquisition CubeSat. Its solar occultationdata will be used to calculate aerosol concentrations in the Earth’s atmosphere. This project will span several yearsfrom launch until the satellite falls out of orbit and burns up in the atmosphere. The complete mission CONOPS forthe NanoSAM project, from launch (Step 1) to burning up in Earth’s atmosphere (Step 9), is illustrated in Fig. 2.After launch, the CubeSat will be deployed into a low-Earth-orbit (LEO) of 500 km using a CubeSat deployer suchas Nanoracks or similar. Once in orbit, the NanoSAM CubeSat will boot-up and perform a bus checkout to ensurethat all subsystems are operational. Once the spacecraft verifies its functionality, it will begin its solar occultationdata acquisition process. This includes the prediction of the location of a sunrise/sunset event. Then, the satellite willvertically scan to measure the irradiance of the Earth’s atmosphere at 1.02 µm through a narrow spectral band. Oncemeasurements are collected, the irradiance data will be converted from an analog signal to a digital signal, packetized,and stored for later transmission. When the NanoSAM CubeSat passes over designated ground pass locations, it willdownlink the collected irradiance measurements for post-processing at ground stations. The NanoSAM CubeSat willcontinue to take measurements over its mission lifetime until the spacecraft de-orbits and burns up in the Earth’satmosphere.Figure 2. General NanoSAM CONOPSThe student team’s objective for the initial year of the Ball Aerospace project is to design, build, and test an opticalinstrument intended for integration into the NanoSAM CubeSat. The optical instrument will consist of optics and anelectronics system with ancillary software. The student team’s testing CONOPS is illustrated in Fig. 3.09/30/197 of 51University of Colorado BoulderCDD

Figure 3. NanoSAM Team Testing CONOPS for This Year’s ProjectThe team will begin testing the optical instrument in a dark room with a 0.25 W LED representing the Sun as aradiation source. A laptop computer will be used to communicate with the optical instrument and direct when theinstrument should collect data. With the instrument powered on, a 0.25 W LED, simulating a sunrise or sunset event,will be pointed towards the instrument and focused through the optics system. A 1.02 µm filter will filter the radiatedlight before reaching a photodiode detector located within the instrument. To verify that the photodiode is detectingthe incoming light, the change in the photodiode’s electrical properties will be observed. A trans-impedance amplifierwill then convert the signal produced by the photodiode to a voltage signal. An analog-to-digital converter will convertthe analog voltage signal to a digital voltage signal for data packetization and storage in the instrument. Finally, theirradiance data will be transferred to a laptop computer for further data analysis.2.4.Functional Block DiagramFig. 4 shows the complete functional block diagram for NanoSAM. The team will only focus on producing thecomponents within the red dashed box on the right side of Fig. 4. The components will form the payload consistingseveral elements. An optics system will utilize an optical bandpass filter and a reflector to filter and focus on thesunlight through the atmosphere.09/30/198 of 51University of Colorado BoulderCDD

Figure 4. NanoSAM Functional Block Diagram2.5.Functional RequirementsThe NanoSAM project contains 7 functional requirements that will flow down to top-level design requirements. Thefunctional requirements are listed below while the other levels of requirements can be found in section 3 of the document.1. The payload shall detect and measure solar attenuation via the solar occultation method. Verification: The payload will be tested in a simulation of the solar occultation method by measuring solarattenuation at various points in the day when the sun is obscured by varying amounts of atmosphere.2. The payload shall predict the location of the sun to initiate a data capture sequence. Verification: The predictions of the sun’s location will be verified by analysis in a physics-based softwaresuch as STK or GMAT.3. The payload shall self-calibrate before or after each data capture instance. Verification: The instrument will be tested with a known radiation source such as lasers or LEDs in a darkroom to ensure the measured data matches theoretical & manufacture data for the known source.4. The payload shall collect and store solar attenuation data. Verification: The instrument will be tested with a radiation source to verify that data was collected andstored.5. The payload shall be able to be commanded from an external source. Verification: The payload will be tested by uploading commands to it via a laptop.6. The payload shall draw no more than 4.5 W at any instant. Verification: The power consumed by the payload can be measured during testing and through calculations.7. The payload shall be compatible with an off-the-shelf CubeSat bus or bus architecture.09/30/199 of 51University of Colorado BoulderCDD

Verification: The compatibility will be verified by testing the payload in a mock CubeSat bus or busarchitecture.3.Design RequirementsThe complete set of requirements for the team’s NanoSAM project can be found in Tables 2, 3, and 4 below. TheLevel 0 requirements are the functional requirements that were also mentioned in Section 2.5 above. These functionalrequirements were used to derive the Level 1 and Level 2 requirements shown in subsequent tables. The orbital andground station parameters used to determine some of the values for various design requirements are shown in Table 1.In order to ensure that all of the requirements that were developed are verifiable, a Requirements Verification Matrix(RVM) was created. This RVM can be found in is Tables 5, 6, and 7 below.ParameterOrbit AltitudeOrbit EccentricityOrbit InclinationOrbit Right Ascension of the Ascending NodeOrbit Argument of PerigeeGround Station LocationMinimum Contact Elevation AngleValue500 km0 (circular orbit)45 0 0 40.11 N, 105.27 W15 Table 1. Orbital and Ground Station ParametersThe orbital and ground station parameters for a mission starting on January 1st, 2021 at 12:00 am resulted in severalcontact times and duration that lasts 7 days. A table of these contact times and duration can be found in Appendix 7.2.From these results, there were on average 5 contacts per day with an average duration of 332.24 secondsa .a These values were obtained using NASA Goddard’s General Mission Analysis Tool (GMAT) with a default Earth Gravitational Field Propagatorand Model.09/30/1910 of 51University of Colorado BoulderCDD

0Solar ent TextLevel 0The payload shall detect andmeasure solar attenuation viathe solar occultation method.The payload shall predict thelocation of the sun to initiate adata capture instance.The payload shall self-calibratebefore or after each datacapture instance.RationaleThis method for measuring solarattenuation was specified by the customer.In order to start a data capture instance theoptics must be pointed at the sun.Solar radiation can vary in magnitude dueto the elliptical orbit of Earth. A baselinemeasurement of an unattenuated radiationsource for each data capture instance willensure the instrument is calibrated.Data StorageThe payload shall collect &Solar attenuation data is the critical datastore the solar attenuation data.being taken by the instrument and willneed to be collected and stored for futurepurposes.CommandingThe payload shall be able to be The payload is not a standalone device andcommanded from an externaltherefore needs to receive commandssource.externally from a ground systemAverage PowerThe payload shall draw anThe power required for the CubeSat toDrawaverage of 4.5 W over an entireoperate should be within reason and asorbit.low as possible to make sure that thepower budget will be valid. [12]BusThe payload shall beThe customer specified that the systemCompatibilitycompatible with an off-the-shelfmust be compatible with a CubeSatCubeSat Bus/Bus ArchitectureBus/Bus Architecture. The exact size wasnot specified as the size of the instrumentwas unknown at the proposal of theproject.Table 2: Level 0 Requirements Flow Down Matrix11 of 51University of Colorado BoulderCDD

e optical system shallmeasure solar attenuation at acenter wavelength of 1.02micron with a bandwidth of 40nm1.3SNR2.1GroundComputationThe payload shall have asignal-to-noise ratio (SNR)between incoming photons andthe instrument of 1.2 · 104 orgreater. [16]The external command sourceshall predict solar location andassociated payload pointing.3.14.15.15.26.17.17.209/30/19Requirement TextLevel 1The payload shall have afield-of-view of 1.3 arcminutes.RationaleWhen placed in a 500x500 km circularorbit the field-of-view must be 1.3arcminutes to achieve 1 km verticalresolution.This is a wavelength at which aerosolparticles can be detected. Otherwavelengths at which aerosol particles canbe detected have interference from otherconstituent absorption or Rayleighscattering.This SNR will ensure the data has anacceptable level of noise to obtainscientifically accurate measurements.By doing the calculations required topredict solar location and associatedpayload pointing via an external commandsource the onboard computer will requireless capability.BaselineThe instrument shall measureSolar attenuation can be calculated using aan unattenuated radiationdecibel system by comparing ansource to obtain a baselineunattenuated baseline measurement to anmeasurementattenuated data point.Storage SizeThe instrument shall collect andThis storage size will ensure that no datastore attenuation data for 2 days will be lost in case of two missed downlinkminimum.opportunities. This ensures future work onthe project will have adequate storage incase of missed downlink opportunities.CommandThe payload shall be able toUplink opportunities might be missed soStoragestore 15 commands at one time.the payload will need to store commandsuntil the next window of opportunity. 15commands is the minimum number ofcommands needed to operate.CommandThe uplink of commands to theThe time it takes to transfer data betweenTimepayload shall take no longerground systems and payload will affectthan 150 seconds.how much data it can send over oneground pass. 150 seconds is slightly lessthan 1/2 of the average ground pass.MaximumThe payload shall draw no moreThe maximum voltage used by theVoltagethan 7.1 VDC.instrument needs to be specified to makesure that the electronics components arenot short-circuited.PayloadThe payload shall have volume This ensures the payload will fit within theVolumedimensions no greater than thatchosen CubeSat form factor to allow forallotted in the chosen CubeSatfuture work to continue within theform factor.customer’s specification of compatibilitywith a CubeSat Bus/Bus Architecture.Payload MassThe payload shall have a massThis ensures the mass of the payload andno greater than that alloted inbus will be less than the maximumthe chosen CubeSat form factor.allowable mass for the chosen CubeSatsize.Table 3: Level 1 Requirements Flow Down Matrix12 of 51University of Colorado BoulderCDD

5.2.1Requirement TextLevel 2The optical system shall havean aperture of at least 3.29 mm.The optical system shall utilizea filter with a center wavelengthof 1.02 micron with abandwidth of less than 40 nm.The external command sourceshall predict the time at which adata capture instance isinitiated.The external command sourceshall predict the time at which abaseline measurement will betaken.RationaleThe specified aperture will allow thepayload to achieve the desired FOV.A filter will ensure that only the desiredwavelength of light will be measured.The payload will not have to calculatewhen to initiate a data capture instanceand will instead be commanded to startcapturing data.TimeThe payload will not have to calculate theComputationtime at which the baseline measurement is(Baseline)taken and will instead be commanded totake the baseline measurement at apre-determined time.TimeThe external command sourceThe payload will not have to calculateComputationshall predict the time at which awhen to terminate a data capture instance(Termination)data capture instance isand will instead be commanded toterminated.terminate data capture.Baseline TimeThe instrument shall captureThe instrument will capture the baselineand store the baseline data atdata at the commanded time to comparethe commanded time.all other data points during that specificdata capture instance to.Command SizeThe payload shall be able toThe payload will need to receive enoughreceive 15 commands at time ofcommands at time of downlink/uplink sodownlink/uplink.that if two downlink/uplink opportunitiesare missed the payload will be able tocontinue its function. This will allow foran entire new set of commands to beuplinkied.Table 4: Level 2 Requirements Flow Down MatrixThe verification methods for all levels of the requirements can be found in Tables 5, 6, and 7. These tables areorganized according to the levels of requirements. The X’s in the tables within the verification method represents theapproach used to ensure that the project meets the requirements. A brief description is also provided in the tablesunder verification method breakdown. Additionally, the description provided in the Level 0 Requirements Flow DownMatrix (Table 2) are equivalent to the information in Section 2.5 of the functional requirements.09/30/1913 of 51University of Colorado BoulderCDD

RequirementIDRequirementTitleTest1.0Solar OccultationX2.03.04.05.06.07.009/30/19Verification MethodAnalysis InspectionLevel 0Verification Method BreakdownThe payload will be tested in asimulation of the solar occultationmethod by measuring solar attenuation atvarious points in the day when the sun isobscured by varying amounts ofatmosphere.Solar PositionXThe predictions of the sun’s location willbe verified by analysis in a physics-basedsoftware such as STK or GMAT.CalibrationXThe instrument will be tested with aradiation source to verify that data wascollected and stored.Data StorageXThe instrument will be tested with aradiation source to verify that data wascollected and stored.CommandingXThe payload will be tested by uploadingcommands to it via a laptop.Peak Power DrawXXThe power consumed by the payload canbe measured during testing and throughcalculations.Bus CompatibilityXThe compatibility will be verified bytesting the payload in a mock CubeSatbus or bus architecture.Table 5: Level 0 Requirements Verification Matrix14 of 51University of Colorado BoulderCDD

5.15.26.17.17.209/30/19TestVerification MethodAnalysis InspectionLevel 1XVerification Method BreakdownThe field-of-view will be calculatedusing equations.WavelengthXXThe center wavelength can be verifiedthrough inspection while thebandwidth can be calculated.SNRXThe SNR can be calculated bymeasuring the signal power and thenoise power.Ground ComputationXCalculations will be performed inGMAT/STK.BaselineXThe instrument will be tested with aknown radiation source at maximumintensity to simulate an unattenuatedmeasurement. The intensity will bedecreased and additional readings willbe taken, simulating attenuatedmeasurements.Storage SizeXThe instrument will be tested with aradiation source and data will becollected and stored. This test willcapture an amount of data that willcorrespond to 7 days of on orbitoperation.Command StorageXThe payload will be connected to alaptop and run with commandsuploaded to ensure the commands areproperly stored and followed.Command TimeXThe payload will be connected to alaptop which will supply commands.The upload time per command will berecorded.Maximum VoltageXXThe voltage can be measured using avoltmeter.Payload VolumeXThe payload’s volume will becalculated in a modeling software.Payload MassXThe payload will be be measured to atleast 1 decimal place.Table 6: Level 1 Requirements Verification Matrix15 of 51University of Colorado BoulderCDD

ter2.1.12.1.22.1.33.1.15.2.14.4.1.TestVerification MethodAnalysis InspectionLevel 2XXXVerification Method BreakdownThe aperture can be verified by calculations.The center wavelength can be verifiedthrough inspection while the bandwidth canbe calculated.TimeXA Simulation will be performed inComputationGMAT/STK in conjunction with ground(Initiation)based testing.TimeXA Simulation will be performed inComputationGMAT/STK in conjunction with ground(Baseline)based testing.TimeXA Simulation will be performed inComputationGMAT/STK in conjunction with ground(Termination)based testing.Baseline TimeXA Simulation will be performed inGMAT/STK in conjunction withground-based testing.Command SizeXThe payload will be connected to a

GMAT General Mission Analysis Tool InGaAs Iridium, Gallium, Arsenic LEO Low Earth Orbit NanoSAM Nano-Stratospheric Aerosol Measurement . The general concept of operations (CONOPS) for the NanoSAM CubeSat project proposed by Ball Aerospace includes the design, construction, launch and operation of a solar occultation data acquisition .