‹#›
GP-B, 2004-2005 Relativity Mission, Gravity Probe B
STAR 2015 Space Time
Asymmetry Research
LISA, 2025 Laser Interferometer Space Antenna
Gravitational Physics
Experiments in Space
Sasha Buchman Stanford University
Lisbon & Porto, 2010
‹#›
George Bernard Shaw 1930
Ptolemy made a universe which lasted 1400 years,
Newton also made a universe which has lasted 300 years,
Einstein has made a universe and I can’t tell you how long that will last
Napoleon and other
great men of his
type, they were
makers of empire,
but there is an order
of men who get
beyond that.
They are not
makers of empires,
but they are makers
of universes.
And when they
have made those
universes, their
hands are unstained
by the blood of any
human being on
earth.
‹#›
Outline
Why Test Gravity ?
How To Test Gravity ?
Why Space ?
General Relativity, GP-B
Lorentz Invariance, STAR
Gravitational Waves, LISA
Gravity
Strong Nuclear Force
Weak Nuclear Force
Electro Magnetism
Balloon experiment
GP-B
LISA
STAR
‹#›
How Well Is GR Tested
Einstein's 2½ tests
Perihelion of Mercury, light deflection, redshift ( ½ test)
Test enabled by new technologies since 1960 Clocks, electromagnetic waves, massive bodies
Observations [O] vs. controlled physics experiments [E]
New non-null tests Shapiro time delay [O]
Geodetic effect by laser lunar ranging [O]
Binary pulsar, gravitational wave damping [O]
Gravity Probe A [E]
Gravity Probe B [E]
The Eddington PPN formalism & new null tests LLR, Nordtvedt effect restricts scalar-tensor theories [O]
Earth tides, Will effect eliminates Whitehead's theory [O]
GW astronomy [50 years since J. Weber detector]
GM/c2R << 1
Sun ~ 2 x 10-6 ; Earth ~ 7 x 10-10 ; 1 m W sphere ~ 5 x 10-21
Einstein 2½ Tests
The General Theory of Relativity:
Is THE Accepted Theory of Gravitation
Agrees to Better than 10-4 – 10-5 with Experimental Results
‹#›
Why Verify GR ?
General Relativity = Present Theory of Gravity
Mathematically Consistent
Agrees with Observation (so far)
Unified Physics ?
Standard Model: Quantum Gauge Theories
GR cannot be quantized
Partial steps toward Grand Unification
Strings/super symmetry
Damour - Polyakov
Experimentation and Observation
Gravity
Strong Nuclear Force
Weak Nuclear Force
Electro Magnetism
‹#›
Problems With GR ?
Astronomical Observations
A Dark Universe
An Expanding Universe
“Interesting” Phenomena
Solar System Observations ?
Pioneer Anomaly
Fly-by Anomaly
Short Scale Deviations ?
NGC 6251
Power 1038 W (1012 Suns)
Jet aligned 107 light years
GP-B science
Expansion of the
Universe Over Time
?
‹#›
How To Test Gravity ?
Astronomical Observations
CMB Polarization: WMAP, BOOMERANG
X Ray Polarization: GEMS
Pulsar Timing
Space Experiments
Gravitational Waves: LISA, DECIGO, BBO
Rotational Effects: GP-B
Space-Time Isotropy: STAR, OPTIS
Equivalence Principle: MICROSCOPE, STEP
Laboratory
Short Scale Deviations
Gravitational Waves: LIGO, VIRGO, Antennas
High Frequency GW
Gravity and Extreme
Magnetism (GEMS)
Boomerang
WMAP
Drag-free
Test Mass
High-Finesse ULE
Cavity Resonators AGIS Atomic Gravitational
Wave Interferometric Sensor
‹#›
Why Go To Space?
Seismic Noise @ f < 10Hz
Low gravity
Varying gravitational potential
Long baselines
“Fast” varying velocity vector 7 km/a @ 1.5 h vs. 0.4 km/s at 24 h
Long measurement times
Launch environment
Thermal environment
Cost and duration
Reliability; one shot
Communications bandwidth
‹#›
Drag-Free Technology
GP-B Flight Gyroscope 2004
TRIAD Sensor 1972
Control Spacecraft to follow an inertial sensor
Reduce disturbances in measurement band
Aerodynamic drag
Magnetic torques
Gravity Gradient torques
Radiation Pressure
‹#›
Why Test Gravity?
How To Test Gravity ?
Why Space ?
General Relativity, GP-B
‹#›
The Relativity Mission Concept
Geodetic Effect Space-time curvature
de Sitter (1916)
ee R
R
R
Rc
GIR
Rc
GM
232
1
32
3
241
2
1v
Controlled experiment
Frame Dragging Rotating matter drags space-time
Pugh and Schiff (1959, 1960)
"No mission could be simpler than Gravity Probe B.
… just a star, a telescope, and a spinning sphere." — William Fairbank
PPN Parameters
= 1 in GR
curvature of space
1 = 0 in GR
preferred frame effect
‹#›
Basis for 106 advance in gyro performance
Space
reduced support force, "drag-free"
roll about line of sight to star
Cryogenics
magnetic readout & shielding
thermal & mechanical stability
ultra-high vacuum technology
The GP-B Challenge
Gyroscope (G) 106 better than best 'modeled' inertial navigation gyros
Telescope (T) 103 better than best prior star trackers
Gyro Readout calibrated to parts in 105
G – T <1 marc-s subtraction within pointing range
‹#›
Main Experimental Features
Electrostatically suspended quartz gyroscopes with He spin-up
< 0.3 marcsec/yr drift
Telescope with cryogenic photo detector read-out pointed
<0.1 marcsec measurement, < 34 marcsec/Hz pointing
Drag free satellite in 642 km polar orbit, rolling at 5 mHz
<10-10 g, <10-12 g transverse
Cryogenic experiment 2K superfluid helium
>18 month lifetime
London moment based read-out with dc SQUID amplifiers
<200 marcs/Hz, <810-29 J/Hz
Superconducting magnetic shielding
< 510-7 G, >1012 total ac attenuation
All (almost) requirements met
‹#›
The GP-B Science Instrument
Mounting
flange
Quartz
block
Guide star
IM Pegasi
1 2
3 4
Gyros 3 & 4
Gyros 1 & 2 Star
tracking
telescope
Field of View: ±60 arc-sec.
Meas. noise: ~ 34 marcs/√Hz
SQUID Magnetometer (1 of 4)
Measurement noise: ~ 200 marcs/√Hz
SIA
‹#›
GP-B Systems
Probe Test of probe in dewar
Thermovac test of spacecraft
‹#›
GP-B Launch April 20, 2004
‹#›
The GP-B Gyroscopes
Fused quartz rotor R/R < 10-6
Quartz housing R/R < 10-5
Electrostatic suspension 10-9 g to 1 g
Capacitive positioning <0.3 nm at roll
He gas spin-up 60 - 80 Hz
UV charge control <15 pC
Electrical Suspension
He Gas Spin-up
Magnetic Readout
Cryogenic Operation
‹#›
A. Initial Orbit Checkout - 128 days
Re-verification of all ground calibrations [scale factors, tempco’s etc.]
Disturbance measurements on gyros at low spin speed
B. Science Phase - 353 days
Exploiting the built-in checks [Nature's helpful variations]
C. Post-experiment tests - 46 days
Refined calibrations through deliberate enhancement of
disturbances, etc. […learning the lesson from Harrison & Cavendish]
GP-B Science Mission 3 Phases
Anomaly 1 (Phase A, B) – Polhode-rate variations affect Cg determinations
Anomaly 2 (Phase B, C) – Larger than expected misalignment torques
Detailed calibration & data consistency checks eliminated many
potential error sources & confirmed many pre-launch predictions, but…
‹#›
A. Polhode period variations affect
scale factor (Cg) determinations
Observed in early science phase
B. Misalignment torques: req. 103
Observed in post-science calibration
C. Roll-polhode resonance torques
Observed in data analysis phase
3 Data Analysis Issues
All due to one physical cause:
The Patch Effect
Gyro 2 per orbit orientation
142 139 140 141 145 144 143 138 146
sEW
res. m
EW
orie
nta
tio
n,
s EW (
arc
se
c)
Date (2005)
0 0.2 0.4 0.6 0.8 10
0.5
1
1.5
2
2.5
3
3.5
4
Angle of Misalignment (degrees)
Dri
ft R
ate
(as/d
ay)
Magnitude of Drift Rate vs. Angle of Misalignment
Gyro 1
Gyro 2
Gyro 3
Gyro 4
140 190 240 290 340 390 440
4
3
2
1
Gyro 1 Polhode Period
Time (days from Day #1; Apr. 20, 2004)
H
ou
rs
‹#›
RESONANCE Repeat events
to 200 marcs
LINEAR DRIFTS Apparent linear drift
about 500 marcs/yr
MISALIGNMENT
Roll averaged
1,000 to 2,500 marcs/yr
GP-B Performance
DESIGN
100
10
1
0.1
0.01
1000
marc
sec
/yr
6,606 Geodetic effect
39.0 Frame dragging
effect
0.50 GP-B
Requirement
‹#›
Relativity
Misalignment
torque Roll-polhode
resonance torque
Add misalignment torque term to equations of motion
Add roll-polhode resonance term to equations of motion
Relativity & Newtonian
Torque Model
‹#›
Effects of Patch Potentials
Observations explained by patch effect of
~50 - 100 mV on rotor and housing
8 Observed Effects
1. Coupling to GSS
Z axis force
2. At zero frequency
3. At polhode harmonics
Torques
4. Misalignment
5. Resonance
Dissipation mechanisms
6. Polhode damping
7. Spin-down
8. Charge meas. bias
Affects read-out performance
Affect gyro performance
‹#›
Raw Flight Data (Gyro 2)
Apply Torque Model
‹#›
Newtonian Effects
Removed
Jan 8 Jan 28 Feb 17 Mar 9 Mar 29 Apr 18 May 8
Jan 8 Jan 28 Feb 17 Mar 9 Mar 29 Apr 18 May 8
date (2004)
–0.5
0.0
0.5
1.0
1.5
2.0
1.64
1.66
1.68
1.70
1.72
1.74
EW
orien
tation (
arc
sec)
NS
orienta
tion (
arc
sec)
EW uniform drift
NS uniform drift
Gyro 2, orientations – Newtonian torques
–1
+1
‹#›
Gyro 1 Segments
Consistency
NS / EW observability varies due to annual aberration
Seg. 2-3
Seg. 9
Seg. 5-6
Seg. 10
95% confidence ellipses
Seg. 5,6,9,10
‹#›
Four-Gyroscope
Consistency
Gyro 2
Gyro 4
Gyro 3
Gyro 1
Gyros
1,2,3,4
95% confidence ellipses
‹#›
1 marcsec/yr = 3.2×10-11 deg/hr = 1.510-16 rad/sec
Gyroscope Performance
ma
rcs
ec
/yr
105
106
107
108
109
1010 Electrostatic gyro
uncompensated
(10-1 deg/hr)
Electrostatic gyro
with modeling
(10-5 deg/hr)
Spacecraft gyros
(3x10-3 deg/hr)
Laser gyro
(10-3 deg/hr) Expected GP-B
104 -105 improvement over previous gyroscopes
39 Frame dragging effect
6,606 Geodetic effect
~ 1,000 Patch effects
GP-B Gyro Design m
arc
se
c/y
r
103
102
10
1
10-1
104
10-6
10-6
‹#›
GP-B Summary
GP-B worked very well
All systems performed beyond expectations
Anomalous effects
Explained by patches on rotor and housing
Systematic errors ~ 10 marcs
Complex experiments in space work
Surprises can be overcome: patch modeling
‹#›
Why Test Gravity?
How To Test Gravity ?
Why Space ?
General Relativity, GP-B
Lorentz Invariance, STAR
‹#›
Gravitational Science
on Small Satellites
GOALS
Gravitational experiments (+others?)
Lorentz invariance
Fundamental constants in variable potential
Small satellite missions
180 kg, 150W
60 M$, < 6 years
Education
PhD thesis, undergraduates
Capability continuity
IMPLEMENTATION
STAR program
3-5 projects
Start 2009, first launch 2015
‹#›
Why Measure c Invariance?
Colladay and Kostelecky (1997)
“The natural scale for a fundamental theory including gravity is
governed by the Planck mass MP, which is about 17 orders of
magnitude greater than the electroweak scale mW associated
with the standard model. This suggests that observable
experimental signals from a fundamental theory might be
expected to be suppressed by some power of the ratio:
r ≈ mW ∕ MP ~ 10−17
STAR’s one part in 1017 sensitivity
could close that gap.
STAR = Space-Time Asymmetry Research
‹#›
Kennedy-Thorndike
100 gain over the best KT measurement
R.J. Kennedy E.M. Thorndike
History of KT resolution
KT STAR Mission Objectives
Measure the boost anisotropy of the velocity of light to 10-17
Derive KT coefficient to the corresponding resolution, ~ 7x10-19
Readout Description
Orbital velocity varies with respect to CMB.
If c depends on vS relative to CMB, the
resonant frequency of the cavities changes.
Signal at orbital period TKT (TKT ≈ 100 min)
STAR compares the frequency of cavity to
wavelength of molecular-iodine stabilized
laser as absolute frequency reference.
‹#›
Lorentz Invariance
Targeted Outcomes for Astrophysics
1. “Test the validity of Einstein’s General Theory of Relativity;”
2. “Investigate the nature of space-time through tests of fundamental
symmetries; (e.g., is the speed of light truly a constant?)”
NASA Science Plan 2007-2016
Lorentz contraction parameter
time dilation parameter
tests for transverse contraction
GR: c() /c = 1, KT = MM = 0
CMB: preferred frame (vCMB /c)2 = 10-6
1. Test space/time symmetry
2. Improve understanding of cosmological parameters in
Standard Model Extension (SME)
2
22
2
2
2111ccc
c
sin)(
),( vvv
KT MM
‹#›
Component of SME Beat Signal
‹#›
Main Systems
Commercially available
components reduce risk
and keep STAR low-cost
Iodine Gas Cell Absolute
Frequency Reference
1064 nm Nd:YAG Laser
Frequency Shifters
Multi-Layer Thermal Shield for Sub-µK
Thermal Stability of Enclosure High-Finesse ULE
Cavity Resonators
‹#›
Major Mission Characteristics
Measure the anisotropy of the velocity of light to 10-17
Primary data product: map of local values of c
Orbit: most precessing sun-synchronous LEO’s
Launch vehicle: Secondary payload
Altitude: 650 km
Mission duration: One year
Launch: late 2015
Cost: $ 50M
Spacecraft in orbit concept
165 kg
110 W
Lasers/Optics Deck
Electronics
Cavities &
Core Optics
Spacecraft structure
Payload layout
LISA technologies
Iodine clocks
Optical cavities
Thermal enclosure
Frequency doublers
‹#›
Why Test Gravity?
How To Test Gravity ?
Why Space ?
General Relativity, GP-B
Lorentz Invariance, STAR
Gravitational Waves, LISA
‹#›
Gravitational Waves (GW)
In the weak field approximation GW can be represented
as a perturbation to the Minkowski flat space-time:
g Minkowski space perturbed by gravitational waves
Minkowski space
h gravitational waves perturbation hg
Using the transverse traceless gauge the field equation for h is:
S Energy densities and stresses
2 1
c2
2
2t 2
h
G
c4S
In GR h results in two plane waves with polarizations at 45°:
h a ˆ h t z
c
b ˆ h t
z
c
‹#›
Gravitational Radiation: The Quadrupole
Space is “stiff” (2G/c4 = 1.710-44 s2kg-1m-1)
The GW perturbation h propagates as 1/r
The quadrupole is the first gravitational radiation moment
The leading gravitational radiation term is
h Minkowski space perturbation
G gravitational constant
r distance to the source
Q trace-free quadrupole tensor
..124
Qrc
Gh
‹#›
LISA Concept
Three spacecraft in triangular formation separated by 5 million km
Spacecraft have constant solar illumination
Formation trails Earth by 20°
Orbit position and velocity modulate GW amplitude and phase
From amplitude and phase LISA determines direction to source to <1°
‹#›
The LISA Gravitational-Wave Sky
‹#›
Gravitational Waves Through Time
‹#›
The GW Spectrum
Bar Detectors
HF EM Detectors
BBO
DECIGO
‹#›
The Earth Based GW Detectors
GW Detection by 2015-2020
‹#›
LISA Systems
Payload Spacecraft Propulsion
module Launch
configuration
Y tube Optical bench Test mass
‹#›
LISA Path Finder Development
GRS Housing Torsion balance
Optical components Optical bench
‹#›
Two Optical Benches in Spacecraft
‹#›
Space GW Missions
LISA
2025
Arms are 50,000 km
LISA II
20??
LPF
2013
‹#›
Conclusions
GR most likely needs updating
GP-B shows that complex experiments in space do work
GW space observatory should be functional next decade
STAR could see first LIV this decade
Space science can and will be done on ‘small’ missions
Gravitational experiments are “taking off” in the next decade
‹#›
Looking to the Future
The towering figure of Einstein
provides a tempting target for
physicists of all stripes.
He would perhaps look with
approval on these efforts to go
beyond his theories.
The Search for Relativity Violations
Alan Kostelecky
Scientific American 2004
‹#›
‹#›
GP-B Back-up
‹#›
Gravitoelectric and
Gravitomagnetic Viewpoint
Similarity between electromagnetism and
General Relativity in weak field and slow motion limit
Space-Time
Metric
Newtonian
Analog
EM
Analog
Gravito-EM
Analog
Rotational
Effect
g00 V Eg 1/3G
g0i No analog Ai Bg FD
gij No analog No analog No analog 2/3G
‹#›
“Near Zeros” Technologies
6
4
Seven Near Zeros for Gyro Performance
Rotor inhomogeneities < 10-6 met
Rotor asphericity < 10 nm met
"Drag-free" (cross track) < 10-11 g met
Magnetic field < 10-6 G met
Pressure < 10-12 torr met
Electric charge < 15 pC met
Electric dipole < 0.1 Vm issue 2
1
3
5
‹#›
Rotor Fabrication
Profile of
Optical Path Difference - nm
Holder for Quartz
Homogeneity Measurement
Polishing System
Roundness
Measurement
Surface Profile Scaled to Earth Size
Radius 1.9 cm
Homogeneity < 2 ppm
Sphericity < 1 ppm
Mass unbalance < 1 ppm
I/I < 310-6
Nb Film Uniformity <2%
Met All
Requirements
Surface Profile
Min=9 nm |Max-Min|=19 nm Max=10 nm
‹#›
Housing Fabrication
Radius 1.9 cm
Sphericity < 10 ppm
6 Electrodes in 3 Orthogonal Pairs
5 Turn Read-out Loop
Channel and Ti Nozzle for Spin-up
7-layer Ti-Cu Electrode Coating
3-layer Ti-Cu-Ti Support and
Spin-up Lands Coatings
Ti Film For Bare Quartz
Three Layer Film Seven Layer Film SEM Micrograph SEM Micrograph
Gyro to Spacer Assembly
Spin-up Half Read-out Half
Fused-Quartz Gyroscope Housing
Gyro insertion in Quartz Block
Lands Coatings
Electrodes Coatings
Met All
Requirements
‹#›
Spin-up and Alignment
0 0.5 1 1.50
10
20
30
40
50
60
70
80
90
100
Time (hours)
Spin
rate
(H
z)
Gyro 1
Gyro 2
Gyro 3
Gyro 4
Spin-up of one gyro causes spin
down of other ones: Gyro 1 last
4 Gyroscopes spun to 60-80 Hz
Differential Pumping Requirement
Spin channel ~ 10 torr (sonic velocity)
Electrode area < 10-3 torr
Torque Switching Requirement
Ts, Tr - spin & residual torques
ts - spin time; Ω0 - drift requirement
Tr / Ts < Ω0ts ~ 10-14
First Science Mission Levitation
Gyro #
f (Hz)
df/dt (μHz/hr)
1 79.4 0.57
2 61.8 0.52
3 82.1 1.30
4 64.8 0.28
-250 -200 -150 -100 -50 0 50 100 150 200 250-250
-200
-150
-100
-50
0
50
100
150
200
250
W - E (arc-sec)S
- N
(arc
-sec)
saa-summary-plot.m <GSV median> Contour interval = 25 arc-sec
Gyro1
Gyro2
Gyro3
Gyro4
Spin Alignment to 10 arcsec
Spin speed and spin down meet requirements
‹#›
GP-B on Jon Stewart’s Daily Show
‹#›
GP-B in Flight
GOOD Gyroscopes
104-105 better than ground
SQUID noise meets spec
Trapped magnetic flux meets spec
Charge control ~ meets spec
Position and stability meet spec
τ ~ 7200 to 26000 yr meet spec
Telescope
Meets spec
Dewar
20 months hold meets spec
Orbit within 100 m of ideal
LESS THAN IDEAL Torques
Misalignment torque
Resonance torque
Other
Polhode rate variation
Segmented data
Interference from ECU
SRE scale factor
Systematics &
data grading
New Challenge
‹#›
N-S (Geodetic) E-W (Frame-dragging)
G1
G2
G3
G4
Full Model Results (Dec ’08)
(note: different y-axis scale for N-S vs. E-W)
‹#›
STAR Back-up
‹#›
Michelson Morley Secondary
COSMIC MICROWAVE BACKGROUND
MM STAR Mission Objectives
Measure the anisotropy of c to 10-17
Derive the MM coefficient to ~ 10-11
Derive the generalized coefficients of LIV
• boost independent: < 7x10-17
• boost dependent: ~ 10-13
Readout Description
Compare the resonant frequencies of two
orthogonal high-finesse optical cavities
Signal at 1/2TMM (TMM = 2 – 20 min)
Configuration conceptually similar to MM
History of MM resolution
‹#›
LISA Back-up
‹#›
Gravitational and
Electromagnetic Waves
Gravitational Electromagnetic
Source Coherent mass acceleration
Incoherent charge acceleration
Propagation Space-time oscillations
(2 polarizations at 45°)
EM fields in space-time
(2 polarizations at 90°)
Attenuation None Scattering, absorption
Frequency <10 kHz (possibly higher) >10MHz (radio to gamma)
‹#›
The DECIGO Project
Japanese Space Agency
10-18
10-24
10-22
10-20
10-4 104 102 100 10-2
Frequency [Hz]
Str
ain
[H
z-1/2
] LISA
Terrestrial Detectors
(e.g. LCGT) DECIGO
(Sensitivity: Arbitrary)
‹#›
Advanced Concepts - Stanford
Single spherical proof mass (PM) per S/C
LPF (LISA Pathfinder): 2 cubic ones
Non constraint GRS; 0 of 6 DF (deg. freedom) control
LPF: 9 of 12 DF control
Gravitational sensor separation from S/C Interferometry
LPF: implemented
Fiber utilization
LPF: discrete optics
Reflective optics d/dl 0.1 d/dn
LPF: transmissive optics d/dn10 d/dl
Signal
LO
GRS with double
sided grating for
interferometer and
PM reference
‹#›
Bench Interferometer Configuration
(Example: Polarization Sensitive Grating Beam Splitter)
Proof Mass
Highly simplified
structure compared with
transmissive optics
Laser
Out to
Telescope
In from
Telescope
Detector
Grating
(Other diffraction orders with
detectors not drawn for simplicity)
‹#›
Grating Cavity Displacement Sensing
Sensitivity better than 10 pm/Hz
Goals for Sensor High precision: 1 pm / Hz in LISA band Low power: Less than 20 W optical power Compact: Fiber delivery and read-out
Preliminary Results: 10 pm/ Hz f > 3 kHz
Low-Finesse Littrow Cavities as Displacement Sensors
K.-X. Sun, G. Allen, S. Buchman, D. DeBra, and R. Byer,
Classical and Quantum Gravity 22, S287–S296 (2005)
Patent pending
‹#› Ke-Xun Sun, Sasha Buchman, Robert L. Byer, “Grating Angle
Magnification Enhanced Angular and Integrated Sensors for LISA
Applications,” Journal of Physics CS, 32:167-179, 2006.
Grating Angular Sensor
for Space Missions
Simple construction
No extra optics
No other uncertainty and noise
Experimental Setup
Patent pending
‹#›
Optical Position Determination:
Simulation Spinning sphere, 10 Hz
2 Dimensional
6 Optical sensors
Experimental laser noise
50 nm position noise
50 nm surface roughness
1024 map size
fnoise/fspin = 10-6 3 pm/Hz position noise
‹#›
Utilizing Launch Margins
Technology Demonstrations for the
Gravitational Reference Sensor - GRS
MINISAT, The Mini Satellites
for GRS Technologies
The Program
Frequent launches on ride-along platforms
Standard low cost bus configurations
12 - 24 month project duration
The Benefits
New science: Physical, Life, Engineering
Critical technology demonstrations
Fast advance of NASA mission objectives
Train engineers and scientists for the future
Program Implementation
Collaboration: AMES, Stanford University
Continuity: 1 to 2 missions per year
Total cost per mission: 5 million dollars
AMES
GENESAT
Stanford
NANOSAT
UV LED