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The NanoSat Revolution

The NanoSat Revolution. Robert Sheldon (with thanks to Jim Cantrell) NASA/MSFC/NSSTC/VP62 April 20, 2007. Overview. Review of Jim Cantrell’s 2-day seminar The NanoSat Problem Launcher cost mismatch  complexity Mission Creep  mass increase Bad Attitude  limited functionality

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The NanoSat Revolution

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  1. The NanoSat Revolution Robert Sheldon (with thanks to Jim Cantrell) NASA/MSFC/NSSTC/VP62 April 20, 2007

  2. Overview • Review of Jim Cantrell’s 2-day seminar • The NanoSat Problem • Launcher cost mismatch  complexity • Mission Creep  mass increase • Bad Attitude  limited functionality • The Revolutionary Technology • CCR Laser -- Telemetry • Elliptical Orbit + Spinner • Laser-despun Fast Spinner • Future Applications

  3. Definition of “Sat”  kg.333 0.1kg 1kg 10kg 100kg 1000kg femto pico nano micro small “Smart dust” BMDO (Don’t blame an engineer, it was marketing!) Jim Cantrell, Space Dev Inc, 2007

  4. Smart Dust (Femto /Atto Sats)

  5. Smallsats—the 30,000 ft view • 1985: Smallsats were once considered to be toys • Small-sat conference in Utah in 1988 brought lots of skeptics • Mainly domain of universities and small companies • 1990: Smallsats grew capability in power, pointing and computational capability • 1995: Smallsats become an increasing strong force in the marketplace • 1990-2000: Several small businesses (Spectrum, Ball, DSI) grew capability into mainstream capability • 2007: Smallsats have matured as the major spacecraft providers have all built and flown them: They are the mainstream market • 2008:Nanosats have the same market appeal today that smallsats had 20 years ago Jim Cantrell, Space Dev Inc, 2007

  6. Small Sat Timeline NASDAQ collapse Jim Cantrell, Space Dev Inc, 2007

  7. The Future of Satellite Types What happened to the Nano/Pico? The 2000 NASDAQ bubble in telcomm destroyed most R&D for 7 years. (Due to a slight exponent error in a telcomm report.) Jim Cantrell, Space Dev Inc, 2007

  8. NASA & DoD $/kg scaled (DoD bus mass x 2, $ x 3) Jim Cantrell, Space Dev Inc, 2007

  9. Cost & Launch Impedence Match • The $/kg of a satellite is roughly constant above some fixed cost floor. • The $/kg launch cost has not changed in 30 years ($22/g = Au spot price) in a discretized way--secondary & tertiary payloads are less expensive. • For primary payloads, the smallest launcher puts a fixed cost on a launch (for OSC ~ $20M) though smaller rockets would extend the linearity down to ~100kg payloads. Insurance couples 1) & 2) impedence matched = But we aren’t launching gold, are we?

  10. Launch Cost Jim Cantrell, Space Dev Inc, 2007

  11. Develop / Cost vs. Complexity If cost is fixed, we must maximize productivity = complexity. Time is linear, cost quadratic (N!) with complexity. Failures occur when cost & time are too limited wrt the average. The “gold” is in the labor. No economies of scale. Jim Cantrell, Space Dev Inc, 2007

  12. Mission Creep What is the optimum level of complexity? • Requires linear programming, but real limits are not “hard”, extra time, extra money is available. So we assume a linear or power-law function near the limits, and estimate the optimum point by the first derivative. Here’s a BOTE calculation: $_profit = $_return - $_cost $_returnfn(complexity)fn(telemetry+processing)F(power) $_cost = fn(mass)G(size) Optimum  d$_profit/dL = 0 = dF/dL - dG/dL Some rules of thumb: Density ~1g/cc (thermal, even in miniaturized components) Mass~L3 (Since density is nearly constant) Telemetry~Power (and dish size, but antennae are light) Power~L2 body-mounted solar panels (~massL3 for 3-axis )

  13. Spinner $_profit = k1L2 - k2 L3 d$_profit=(2k1-3k2 L)LdL Optimum SizeL0=2k1/3k2 Smaller is better. 3-axis stabilized $_profit=(k1- k2) L3 d$_profit=(k1- k2) 3L2 dL No Optimum Size! Bigger is always better. Iridium, Teledesic SDO… Optimization Condition

  14. Low-Complexity Spacecraft Complexity index 0-0.33 Small payload mass (~5-10 kg) One payload instrument Spin or gravity-gradient stabilized Body-fixed solar cells (Si or GaAs) Short design life (~6-12 mo) Single-string design Aluminum structures Coarse pointing accuracy (~1-5 deg) No propulsion, no cold-gas Low-frequency communications Simple helix or patch low-gain antenna Low data rate downlink (~1-10 kbps) Low power requirements (~50-100 W) No deployed or articulated mechanisms Little or no data storage No onboard processing ("bent pipe") Passive thermal control with coatings, insulation, etc High-Complexity Spacecraft Complexity index 0.67-1 Large payload mass (~300-500 kg) Many (5-10) payload instruments Three-axis stabilized w/ reaction wheels Deployed sun-tracking solar panels (multi-junction or concentrators) Long design life (~3-6 years) Partially or fully redundant Composite structures Fine pointing accuracy (~0.01-0.1 deg) Mono- or bipropellant w/ 4-12 thrusters High-frequency communications Deployed high-gain parabolic antennas High data rate downlink (Mbps) High power requirements (~0.5-2 kW) Deployed and/or articulated mechanisms Solid-state data recorders (5 GByte) Onboard processing (30 MIPS) Active thermal control with heat pipes, radiators, etc Jim Cantrell, Space Dev Inc, 2007

  15. telemetry shielding lifetime Launch Cost Jim Cantrell, Space Dev Inc, 2007

  16. Attitude = Power • The problem of decreasing telemetry with distance requiring larger amounts of power, is pointing a large dish • Likewise data-gathering satellites improve with pointing, even magnetometers. • This makes attitude control one of the important requirements driving s/c selection, and the major drawback to spinners. • 3-axis nanosats have yet to be built, which means nanosats have low capabilities.

  17. Small Satellite Capabilities Insurgent satellite providers occupy this region of market Market occupied by small university providers and others Jim Cantrell, Space Dev Inc, 2007

  18. NanoSat Applications • NASA • Atmospheric constellations • Station / Shuttle inspection • Exploration initiatives • Component test-beds • Commercial ?? • Researcher testbeds • University testbeds • Small commercial payloads • DoD • GEO SSA • High value asset inspection • ASAT defense [offense?] • Space control • Testbed for ORS components • IC • Distributed sensing • High value asset escort • Communications data exfiltration Applications for nanosats highly dependent upon propulsion and other bus capabilities Jim Cantrell, Space Dev Inc, 2007

  19. Future of Small Sats • Satellite market has followed “disruptive” path over past 20 years • Market disruption is continual and tending towards smaller and more powerful spacecraft • Smallsats are now in mainstream of market • This has been the case for 10 years & expected to continue 5-10 years • Microsats are emerging as capable of addressing the mainstream market • Nanosats are still way below mainstream market demands for capability but offer potential for insurgent provider entry points. • Lower costs remain elusive since the cost of components [COTS subsystems] remains high. [No economies of scale…] Jim Cantrell, Space Dev Inc, 2007

  20. Summary of Nanosat Bias • Nanosats have limited pointing • Nanosats have limited power • Nanosats have limited telemetry • We can shrink a 3-axis s/c with miniaturized components, but we can’t increase a spinner’s capabilities by shrinking (though we do improve it’s profitability). • The breakthroughs have to come in pointing, power and telemetry.

  21. Nanosat Solution #1: CCR (low attitude requirement)

  22. (1996) BU Space Constellation Why do we need a nanosat constellation?

  23. (1996) Space Physics Problem • “The effectiveness of the base-funded space physics research program has decreased over the past decade….The long-term trend that has led to an ever increasing reliance on large programs has decreased the productivity of space physics research.” A Space Physics Paradox, NRC • “Small”, despite being eliminated from the “cheaper-faster-better” triumvirate, is even more essential for survival, not just for Space Physics, but NASA itself. Rob Sheldon, 1996

  24. (1996) Magnetosphere Problem • “The leap from static pictures of averaged structures and cartoon sequences of processes to continuous sequences of global, 3-D, synoptic images of the magnetosphere is widely recognized to be the logical next move in magnetospheric science….The only known way to obtain simultaneous, spatially comprehensive information on data fields of invisible parameters…is through simultaneous multi-point in-situ observations.”G. Siscoe, 96 Roadmap whitepaper • Target Spatial Resolution: Ionosphere =>Magnetosphere • Radial =10% dRe/Re from 5-15 Re --> 12 • Azimuthal = 10% dRe/Re all 360 degrees --> 63 • Vertical (Z) = 1 Re at plasmasheet 0-5 Re --> 6 • TOTAL= 12 x 63 x 6 = 4536 Satellites!!

  25. (1996) Cost: The Bottom Line • Maximum “solar probe” mission = $100 M • Minimum Constellation = 100 satellites • Maximum cost/satellite = $1 M / sat This is a “best case $” mission but not believable. • Typical cost/satellite = $100K / sat Assume 50M$ and 500 satellites as “typical” • Astounding cost/satellite = $10 K / sat This would be a revolution akin to the Model-T (Exactly how many copies to achieve this economy of scale?)

  26. (1996) Launcher Considerations • Launcher Pegasus XL Delta II LEO Mass 550 kg 5,500 kg Volume 5.8m3 63 m3 Area 1.3m2 7.4 m2 Cost $20M $100M • # Satellites 100 500 100 500 Weight 5.5 1.1 kg 55 11 kg Volume 58 11.6 L 630 126 L Area 130 26 cm2 740 148 cm2 Cost/sat $200k $40k $1M $200k

  27. (1996) Miniaturization solution? Detectors/Sensors YES! CPU/DPU YES! Solar Panels Little, 20% Bus/Thrusters Some, 50% Telemetry NO! - 10,000% Multiple satellites will require even faster/wider bandwidth in order to dump the data in 1/100th of the time, with less mass, less size, and less power!

  28. (1996) Solution • We MUST solve the telemetry problem before we can fly a # > 100 constellation • Bandwidth problem was faced by telcomm industry 20 years ago—undersea cables were too limited: Solution? LASERS • We propose to communicate with the satellites using a ground-based laser system, so that the power is on the ground, and the modulation is in space.

  29. (1996) Nanosatellite • Weight: 1kg • Size: 10cm • Power: 1 watt • DPU Motorola603 • Memory: 1 Gbyte • Telemetry : 10kHz • Sensors: 3-axis Mag • 12 pinhole CCD • SEU calibrated RAM

  30. (1996) Deployment • Bus with multiple launchers, kick motors, 3-axis stabilized- “point & shoot” capability • Solid fuel boosters, Spin stabilized, separation avionics, autonomous deployment

  31. (1996) Ground Segment • DSN already saturated • 3 main laser ground stations for 24hr coverage • Radar ground station in Antarctic for polar sat’s. • ~10 Institutional (<100K$) downlinks at interested sites • >90% temporal + spatial coverage of >100 satellites

  32. CCR Nanosat Conclusions • We solved the attitude problem with corner-cube reflectors, which need little attitude • We solved the telemetry problem with lasers. • We solved the power problem by sidestepping it: miniaturize to reduce power, simplify to reduce demand, and move telemetry power to the ground Did it work? Our proposal was funded, and after study we concluded (1998): Not for this application. CCR 1/R4 return! So data from s/c at 8 Re took too much laser power. But  MagCon Mission

  33. (1998) DARPA grant to UCB 650nm laser pointer 2 day life full duty Attitude control?? 4 corner cubes 40% hemisphere Long life

  34. (1998) UCB Corner Cube Top View of the Interrogator Quarter-wave Plate Filter Polarizing Beamsplitter CCD Camera Lens 0.25% reflectance on each surface YAG Green Laser Beam 45o mirror Expander

  35. 300 um (1999) 2nd Try: UCB Monolithic

  36. (1999) U of AZ student project

  37. Nanosat Solution #2: Spinner attitude control

  38. (1999) Elliptical Orbit Telemetry • Put the satellites into elliptical orbits with perigee < 1Re away. Store data. • Use 10m dish on the ground to track the satellite. Dump the data in burst mode at perigee. • No real-time tracking, 5-10 hour delay in updating the “magnetosphere” model. • Larger dishes (e.g., DSN) can provide real-time tracking of a few targets.

  39. (1999)Why Nanosat Magnetometers? • Magnetic fields must be measured in situ • (We too wish we could do it with imaging!) • Magnetic fields must be measured globally • Fields are a global, not local, effect • Magnetic fields must be measured simultaneously • Otherwise space/time ambiguities destroy the image • Siscoe http://rbsp.info/rbs/RbS/PDF/wpaper.html • Magnetic fields must be measured densely • Currents and structure are “narrow” boundary features • The economics of 100’s of satellites => nanosats

  40. (1999) Magnetometer Accuracy • Need better than 1nT sensitivity at L>6 Re This = 1/500 = 0.2% accuracy in magnitude And = 1/2 degree accuracy in pointing • Science goals: Alfven waves, current systems, global models • Nice to have 1nT at L<6 Re as well Requires 1/30,000 = .003% accuracy in magnitude! Requires 1/2 arc-minute accuracy in pointing! • Can nanosats get close to these requirements?

  41. (1999) The Attitude Fix 1/4 wave antenna and magnetometer boom Inside: Batteries, power system, fluxgate mag, CPU, ADC, attitude determination, Cell phone transmitter SPECS: Mass 1 kg Power 1 Watt Spinrate 1 rps Size 15x6 cm 10mm aperature 100mm focal length sun-sensor 2 watt solar-panel 15cm

  42. (1999) 3-Axis Spinners • In traditional satellites, only 2-axes are Fourier sampled, leading to poor resolution along the “z-axis”. • Manfred Boehm (1996) presented and launched an offcenter (nutating) spinner that was able to sample all 3-axes.

  43. (2004) MagCon

  44. Nanosat Solution #3: Laser scan with drag chute positioning

  45. Nanosat Solution • The spinner gives a nice attitude fix, but ruins most of the benefits of a corner reflector except a the poles. That means we’re back to omnidirectional, low datarate radio. Can we recover the laser advantage? • By similar reasoning, a CCR is 1/R4, whereas a lasers at both ends give 1/R2. Can we remotely direct a laser toward us with robust, autonomous control? All laser communicators are feedback stablilized telescopes on massive 3axis platforms. Can nanosats do this? • The answer is a Scanner on a Spinner

  46. (1998) LaserSatCom design $50M10 Gbps cable-in-the-sky. High altitude balloons @10km altitude relay radio through the cloud deck. Electro-Magnetic drag chute Spherical Fresnel Lens Received Signal Toroidal Lens Transmitted signal Laser Detector Scanner

  47. (1999) UCB Try 3: 2D scanning AR coated dome lens Steering Mirror laser CMOS ASIC

  48. (1999) UCB 8mm3 laser scanner Two 4-bit mechanical DACs control mirror scan angles. ~6 degrees azimuth, 3 elevation

  49. (2004) Sensor Array Positioning Because nanosats are small, they lack stored energy, but can use external forces more easily. John Barker, U Glasgow 2004

  50. Applications VLBA, radio/IR telescopes, Planetary reconnaisance, Military warspace-IFF, higher resolution than GPS, unjammable, disposable, quickly deployed… UCB 2001 U Glasgow “Smart Dust”, Planetary exploration, Military sensors

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