D rag and A tmospheric N eutral D ensity E xplorer

1. Drag and Atmospheric NeutralDensity Explorer Colorado Space Grant Consortium and CU Aerospace Engineering SciencesMeeting of the NADIR MURI October 21st, 2008Boulder, Colorado

2. DANDE - NADIR Seminar Overview • Introduction • Science • Instruments • The DANDE Spacecraft • Program Status

3. The University Nanosat Program • University Nanosat – The National Championships of Spacecraft Design • 2 year program in its fifth iteration • 10 out of 30 university proposals selected based on Air Force Relevance • $85k initial seed funding for hardware and student support • In January 2009, one school wins additional $85k, I&T at Kirtland, and flight to Orbit • CU Nanosat Entry • Has involved a core team of graduate students and expanded into 40 graduate and undergraduate students • Many aspects of the ASEN Graduate Projects but organized as independent research and MS research • Has leveraged over $240k from University, Department, DoD, and COSGC Funds I - Introduction

4. Nanosat V Program at CU DANDE will improve atmospheric models and calibrate near real-time models by measuring the following • Deceleration • Atmospheric composition • Horizontal Winds DANDE is spherically shaped to minimize biases resulting from estimation of the drag coefficient I - Introduction

5. DANDE – NADIR Synergies • Provide the information to improve empirical models of neutral density • Determine the relationship between neutral density structure and satellite drag • Understand the physical processes driving the variability of neutral atmospheric density I - Objectives and Requirements

6. Relative Orbit of Two Separating Spacecraft drag induced drift Background and Motivation Storm response of CHAMP E/W winds Scientific understanding hindered by lack of neutral density, composition, and wind measurements Precise orbit prediction depends on accurate knowledge of atmospheric density and in particular excursions from the mean state I - Introduction

7. DANDE Science 7

8. Mission Statement DRAG and ATMOSPHERIC NEUTRAL DENSITY EXPLORER Mission Statement Explore the spatial and temporal variability of the neutral thermosphere at altitudes of 350 - 200 km, and investigate how wind and density variability translate to drag forces on satellites. II - DANDE Science

9. Objectives and Compelling Science Questions Addressed by DANDE II - DANDE Science

10. Objective Requirements Measure in-situ density and composition (O:N2 ratio) during at least 5 sudden geomagnetic storms and 4 periods of quiet geomagnetic conditions in an altitude of at most 350 km and covering a minimum latitude of at least 54 degrees Calibration and validation of models. Goal: also estimate the coefficient of drag in orbit at 350 - 100 km altitude. Measure neutral winds at an altitude of up to 250 km and below and at latitudes of at least 54 degrees during 5 sudden geomagnetic storms and 4 periods of quiet geomagnetic conditions. Provide the wind data with a spatial resolution of at least 500 km (goal: 100 km). Measure large-scale horizontal variations with in-situ density data over the course of at least 5 geomagnetic storms and 4 periods of quiet geomagnetic conditions Develop a low-cost system to make in-situ measurements of the neutral atmosphere and adhere to Nanosat Program Requirements. Finish the proto-qualification unit on time and on budget. II - DANDE Science

11. Minimum Measurement Requirements horizontal resolution of 500km (~64s) 1.SYS26 , composition measurements with resolution of 1.5 m/Δm. Driven by 0.SYS1 and 1.SYS21 (where m/Δm = half peak width at mass m) *percent value based on average conditions during solar maximum, vernal equinox **assuming a wind velocity of 1 km/s, storm conditions II - DANDE Science

12. Goal Requirement Wind and Density Requirement Relationship II - DANDE Science

13. How Measurements are Made Identifying all components of the constituents of the drag equation. With a near-spherical shape, an a-priori physical drag coefficient may be calculated and a physical density can be obtained from the measurements A atmosphere ρ - density VW FD V CD tracking WTS sensor accelerometers solution a priori knowledge a priori knowledge a priori knowledge/ comparison solved II - DANDE Science 13

14. DANDE Science Instruments 14

15. QA-2000 accelerometer x 6 Cost ~$3,000 Precision ng* Bandwidth 6 μHz – 10 KHz** **must be able to reject the larger noise outside of 6 μHz - 1 Hz to achieve 79 ng Accelerometers STAR accelerometer Method to reduce this drift • Flip one accelerometer in positive and negative directions and remove bias • Modulate measurement to 6 μHz - 1 Hzrange • 6 reduces the noise through averaging independent measurements by 0.41 (1/√6) • Provides redundancy Cost ~$3,000,000 Precision 30 ng Bandwidth 10mHz – 100mHz III - DANDE Science Instruments

16. Low frequency bias spin rate ANALOG FILTERING A/D CONVERSION LEAST SQUARES 70 ng Accelerometer Measurement System III - DANDE Science Instruments

17. Problem Description: Measurement System ACC-2 ACC-4 ACC-1 ACC-6 ACC-3 ω ACC-5 R T ACC-2 FD ACC-1 ACC-3 ω = π/3 [rad/sec] ACC-4 PROCESS & AVERAGE ACC-5 ACC-6 III - DANDE Science Instruments

18. 82∘ 82∘ 82∘ -82∘ -82∘ -82∘ 0∘ 0∘ 0∘ 0∘ 0∘ 0∘ 82∘ -82∘ 0∘ 0∘ Accelerometer Analysis Latitude [deg] III - DANDE Science Instruments

19. Wind and Temperature Spectrometer Incoming Neutrals III - DANDE Science Instruments 19

20. Wind and Temperature Spectrometer • Neutral particle (blue) enters the collimator. (Ions rejected) • Neutral particle is ionized inside of a field free electron bombardment region • Neutral particle enters the energy selector and undergoes acceleration towards the exit • Outside the selector, the particle is accelerated abruptly by a -3kV potential towards the Micro-Channel Plate (MCP) • The impact on the MCP causes a cascade of electrons to travel towards one of the anodes which measures the impact. Which anode is triggered depends on the angle at which the neutral particle entered the collimator. III - DANDE Science Instruments 20

21. Wind and Temperature Spectrometer Peak count of vertical distribution ~2000 counts ACC-2 ACC-4 ACC-1 ACC-6 ACC-3 ω ACC-5 # of particles impacting detector R T Angular position about the satellite spin axis, degrees Total number densities across all spectra as the satellite spins W III - DANDE Science Instruments 21

22. WTS Science Data Product Analysis wind angle O wind mag. N2temp. O temp. N2 wind mag. III - DANDE Science Instruments 22

23. Wind and Temperature Spectrometer Will meet science requirements and goals • The error depends on the number of particles registered. • Determined for a true wind velocity magnitude W of 10 m/s: DANDE *from Herrero et. al. unpublished work III - DANDE Science Instruments 23

24. Design Wind and Density Requirement Relationship III - DANDE Science Instruments

25. Density Error – Drag and Wind Data III - DANDE Science Instruments

26. Complex Geometry Effects A behavior different from that of smooth spheres is observed for the faceted spheres. What is the physical drag coefficient of a faceted surface? Physical CDP, partly quasi-specular Physical CDP, 100% diffuse Fitted CD Expected fit Starshine I [Bowman & Moe 2005] III - DANDE Science Instruments

27. Results: Impacts on Starshine Surface Percentage of Total Impacts 0.06 % “latitude” 0.01 % “longitude” 2∘ x 2∘ bins III - DANDE Science Instruments

28. Drag Coefficient of DANDE Bias induced by CD uncertainty using method of [Moe and Moe, 1996] at solar max (2.216 - 2.118)/2.216 = 4.5% III - DANDE Science Instruments

29. Spacecraft Engineering 29

30. Baseline Configuration ESPA Ring DANDE Sphere 18” Lightband Adapter Bracket (LAB) DANDE Overview IV - Spacecraft Engineering

31. Day 2 Day 1 LV SEPARATION AND COMMISSIONING PHASE Wind Composition Acceleration Tracking Tracking Day 9 Day 100 DATA ACQUISITION 1 orbit SCIENCE 1 orbit STANDBY DOWNLINK/UPLINK ~2x in 24 hours ATTITUDE ADJUST ~1 orbit per day RE-ENTRY DYNAMICS ~LAST WEEK OF ORBIT 200 km – 100 km SCIENCE PHASE Mission Timeline • Phase 1: LV Separation and commissioning • Launch Mode - time delay – Safe Mode • Full charge and checkout[18 – 30 hours] • Lightband jettison • Phase 2: Attitude Acquisition • Spin Up [24 h] • Spin-Axis Alignment [120h] • Reserve time [24h] • Phase 3: Science [~90 days] • Science Mode • Standby Mode • Comm. Pass • Attitude Adjust • Repeat IV - Spacecraft Engineering 31

32. Spacecraft Layout IV - Spacecraft Engineering

33. DANDE Attitude • Spin stabilization about orbit normal • 40°/sec (10 rpm) • Only two maneuvers: spin-up and axis alignment • Sensors • Magnetometer for spin-up • Horizon Crossing Indicators for spin axis alignment • Actuators • 2x Torque rods: one along spin axis and one transverse • Passive nutation damper IV - Spacecraft Engineering 33

34. Program Status 34

35. Completed Formal Testing TESTING V - Program Status

36. State of the DANDE Program: Hardware HARDWARE & MANUFACTURING Lessons Learned Engineering Design Unit Competition Review Hardware V - Program Status

37. Integration & Testing Schedule Today Competition Review V - Program Status

38. Questions dande.colorado.edu