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MASTER THESIS Mission and Thermal Analysis of the UPC Cubesat MASTER THESIS Mission and Thermal Analysis of the UPC Cubesat Pol Sintes Arroyo SUPERVISED BY Josep J. Masdemont Soler Universitat Politecnica` de Catalunya Master in Aerospace Science and Technology 14 de desembre de 2009 Mission and Thermal Analysis of the UPC Cubesat BY Pol Sintes Arroyo DIPLOMA THESIS FOR DEGREE Master in Aerospace Science and Technology AT Universitat Politecnica` de Catalunya SUPERVISED BY: Josep J. Masdemont Soler Matematica` Aplicada I ABSTRACT The Project is envisioned as a mission control analysis and a thermal control analysis of the Cubesat that is planning to launch the UPC (Universitat Politecnica de Catalunya). A Cubesat is a 10x10x10 cm cubic satellite that weights no more than 1 kg and that is currently used in many countries and educational institutions as an easy access to space. The primary work to do would be the analysis of the orbit the satellite would perform. In this way, the STK (Satellite Tool Kit) software would provide the mechanism to perform this analysis. Starting with the known values of the project, simulations have been carried out in order to obtain the trajectory the satellite will would perform. Additionally, perturbations in the orbit, comparatives with other models and simulations with different parameters would be studied. All this practical work is completed with a theoretical explanation of what are the models used by the software, what are the parameters used and why we use this ones and no other ones. The second part of the project presents the thermal analysis of the satellite. In this section, draft calculations of the thermal balance of the satellite are presented along with simula- tions with the SEET (Space Environment and Effects Tool) module of the STK. In addition, the necessary theoretical explanations are offered in order to conduct a complete thermal analysis in future projects. Essentially, these two sections plus a theoretical background or state of the art of Cube- Sats or the different types of launches form the Master Thesis. Furthermore, extensive appendixes can be found at the end of the project which act as an ideal complement to the topics presented in the Master Thesis. Results obtained from the simulations show similarities with other related-type projects and with the theory explained. The inclusion of the UPC Cubesat in the existing network of Cubesat developers is advised. HPOP (High Precision Orbit Propagator) is recommended in future simulations. This propagator shows little differences with SGP4 (Special General Perturbations no 4) but although little, these differences can change significantly the orbital elements during a year. Atmospheric drag and the non-spherical shape of the Earth are the ones that affect more the satellite with both secular and periodic changes no matter which orbit is being used. Moreover, among other differences, using the two different shapes of orbit can produce discrepancies in lifetime of 6 or 7 years. On the other hand results from the thermal analysis show variations of temperature from -85oC to 50 oC for the standard case. Important variations are observed with different val- ues of internal dissipation. Finally, the emissivity/absorptivity ratio is the main parameter which we can play in order to change these temperature variations. Table of Contents INTRODUCTION ................................. 1 Chapter 1. Introduction to CubeSats .................. 3 1.1. Definition of a Cubesat ............................. 3 1.2. History of CubeSats .............................. 5 1.3. The CubeSat of the UPC ............................ 7 Chapter 2. Mission Analysis ....................... 11 2.1. Introduction to the STK ............................. 11 2.2. Theoretical background of the orbital dynamics ............... 13 2.2.1. OrbitDetermination . 16 2.3. Perturbation Techniques ............................ 18 2.4. Orbit Prediction ................................. 20 2.4.1. SGP4Propagator . 22 2.4.2. HPOPPropagator . 23 2.5. Ground Track and Accessibility ........................ 24 2.6. Lighting ..................................... 24 2.7. Simulation results ............................... 25 2.7.1. Totalandindividualaccess . 26 2.7.2. Lighting ................................ 29 2.7.3. Orbitshapecomparative . 30 2.7.4. Elevationanglecomparative. .. 32 2.7.5. Propagatorcomparative . 33 2.7.6. Simulationtimecomparative . 37 2.7.7. Satellitelifetime . 37 2.7.8. Orbital elements variation due to perturbations . ......... 40 2.7.9. Dispersionanalysis . 43 Chapter 3. Thermal Analysis ....................... 47 3.1. Theoretical Background ............................ 47 3.2. Simplified results ................................ 50 3.2.1. STKsimulation ............................ 52 CONCLUSIONS .................................. 55 BIBLIOGRAPHY ................................. 57 Appendix A. Cubesat launches and participants .......... 61 A.1. Past launches .................................. 61 A.2. Upcoming launches .............................. 63 A.3. Cubesat participants .............................. 63 Appendix B. Cubesat launch vehicles .................. 67 Appendix C. STK modules ......................... 71 Appendix D. Additional theory for mission analysis ........ 73 D.1. The n-body problem .............................. 73 D.2. The trajectory equation ............................. 76 D.3. Type of conics .................................. 79 D.4. Types of orbit .................................. 80 D.5. Perturbation study ............................... 83 D.6. HPOP force models ............................... 88 Appendix E. STK user’s guide ....................... 91 Appendix F. Simulation tables of the mission analysis ...... 99 F.1. Individual access analysis ........................... 99 F.2. Orbit shape comparative ............................ 101 F.3. Propagator comparative ............................ 102 F.4. Elevation angle comparative .......................... 104 F.5. HPOP vs. SGP4 comparative ......................... 104 Appendix G. Thermal analysis information .............. 107 G.1. UPCSat Information ............................... 107 G.2. Thermal analysis methodology ........................ 108 G.3. Software available ............................... 109 List of Figures 1.1 TypicalCubesat.Source[2]. ... 4 1.2 StandardP-POD.Source[2].. .. 4 2.1 Orbitalelements.Source[12]. .... 17 2.2 Forcestakenintoaccountbyeachpropagator . ....... 21 2.3 Description of the umbra and penumbra effects. Source [17].......... 25 2.4 STK map illustrating all the ground stations of the Cubesat network. Source [STK]....................................... 26 2.5 Number of accesses for all the ground stations during a year(PartI).. 28 2.6 Number of accesses for all the ground stations during a year(PartII). 28 2.7 Totaldurationlightingpercentages . ....... 30 2.8 Number of accesses vs. orbit shape comparative for UPC, NTNU and Malaysia 31 2.9 Lighting properties comparative for a 1200x350 and a 350x350kmorbit . 32 2.10 Accessschemefordifferentelevationangles . ......... 33 2.11 Access comparative for different elevation angles for UPC, NTNU and Malaysia groundstations................................. 34 2.12 Mean access duration/day comparative for each propagator for UPC, NTNU andMalaysiagroundstations . 35 2.13 Lighting properties comparative for each propagator . ............ 36 2.14 SGP4 and HPOP mean access duration/day comparative for UPC, NTNU and Malaysiagroundstationsfora1200x350kmorbit . ..... 37 2.15 SGP4 and HPOP lighting properties comparative for a 1200x350kmorbit . 37 2.16 Apogee, perigee and eccentricity variation during the HPOP 1200x250 km satellitelifetime................................. 39 2.17 i comparative between a spherical (blue) and an elliptical (green) model of Earth 41 2.18 ω comparative between a spherical (blue) and an elliptical (green) model of Earth...................................... 41 2.19 evariationforanellipticalmodelofEarth . ......... 41 2.20 evariationforacomplexmodelofEarth . ...... 41 2.21 evariationproducedbythird-bodieseffects . .......... 42 2.22 Ω variationproducedbythird-bodieseffects . ..... 42 2.23 avariationproducedbyatmosphericdrag . ....... 42 2.24 ω variationproducedbyatmosphericdrag . .. 42 2.25 avariationproducedbySRP. .. 42 2.26 Ω variationproducedbySRP . 42 2.27 avariationproducedbyallperturbforces . ........ 43 2.28 evariationproducedbyallperturbforces . ........ 43 2.29 ivariationproducedbyallperturbforces . ......... 43 2.30 Initial conditions of the dispersion analysis . ............ 44 2.31 Positionofthesatellitessevendayslater . ......... 44 2.32 Finalpositionsofthesatellites . ....... 44 2.33 Range variation between UPCSAT and UPC1 for 50m separation ...... 45 2.34 Range within the satellite will be for a 50m margin . .......... 46 3.1 Incidentlightcharacteristics . ...... 48 3.2 Heat fluxes of a typical satellite orbiting Earth. Source [20]........... 49 3.3 Temperature evolution for the Al. with Kapton with 0.5 W of internal dissipation 54 B.1 Vegalaunchvehicle.Source[6]. .... 69 D.1 Orbitalplaneangles .............................. 78 D.2 Typesofconicsections. 80 D.3 Orbital element perturbation changes. Source [19]. ........... 83 D.4 Nodalregression.Source[19].. .... 86 D.5 Apsidalrotation.Source[19]. .... 86 D.6 Typical dacay of a satellite for a 300 km circular orbit . ........... 87 E.1 STKwindowwithmaincommands. 91 E.2 Period ..................................... 92 E.3 Satellitegeographiccoordinates . ...... 92 E.4 Facilityconstraints
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