Transcript 2009 Olin Student Projects

2009 Olin Student Projects
Keith Gendreau
[email protected]
301-286-6188
Phil Deines-Jones
[email protected]
301-286-6884
Jeff Livas
[email protected]
301-286-7289
2009 Student Projects with
contacts
• Continuation of MCA
– Keith Gendreau
• XACT Sounding Rocket Optical Bench
Alignment System
– Keith Gendreau, Phil Deines-Jones
• UV flux monitor
– Keith Gendreau
• Super Webcam microscope
– Jeff Livas
• USB Bit Error Rate Measuring Tool
– Jeff Livas
Continuation of MCA project
from 2008
• In 2008, I asked the Olin students to
make a “$25 MCA” to measure
pulseheights and record times of X-ray
events from a detector.
• System nearly worked, but not quite…
A PIC Microcontroller Based
Pulse Detection and
Measurement System
Take an input analog signal, look for pulses above a
threshold, detect the peak voltage of each pulse, digitize
the peak voltage, write to a file the pulse time and peak
pulse height, continue….
Build on last year’s “Flux Meter”, if possible.
X-ray Detection and Pulses
X-ray photons
Vsignal
X-ray Detector
Amplifier
X-rays pack a lot of energy. X-ray detectors see
individual X-ray photons. If the detectors and
electronics are good enough, they can determine
the energy of the photon.
Science is to be gained by knowing the energy of
the photons and when they arrived.
Pulses on an analog signal
(from an X-ray detector)
V
vpulse
Vpulse is proportional
to Energy of photon
Pulse widths: ~25 ns- 2µsec
t
tpulse
V
Noise pulses?
vthresh
t
Pulse#1
Pulse#2
Pulse#3
Desired Layout: Top view
Analog signal
From X-ray
Detector
On a BNC
Connector
Olin Pulse
Height Box
USB Output
Computer
With Olin
Software
To display/save
Events
Any type of computer, PC or Mac
(I prefer Mac, but whatever is doable)
Knob for
Additional
gain
Knob for
Lower Voltage
Threshold
Requirements
• Must handle pulses ranging from ~< 100 nsec
to ~ 100 microsec wide
– Loosen requirement: Require 1-50 microseconds
with a goal of 100 nsec to 100 microseconds
• Goal of achieving ~106 counts per second
(typically, it is much less than this, I’d be
happy with ~104 cps)
– Loosen requirement to ~1000 cps with a goal of
105 cps
• Should be able to handle pulseheights
ranging from ~0 to 10 volts (positive).
Output Desires
• ASCII file with time and pulseheight for each event
above threshold
• Plot with histogram of pulseheights
• Flux vs time (like on the flux meter)
• Be creative.
• TCP/IP port?
• eg, The computer reading the instrument can
make the data available as a server to others as
client computers via a TCP/IP Sockets protocol
• Would be an extremely useful feature for beamline
work.
For 2009
• I will send you home with a detector
• We could not get the software to work
from last year.
• Last year’s board broke at the USB
connection and we now have a flaky
USB board on one of our computers…
(QA)
Project #2, XACT Optical
Bench Alignment
• We are in the initial phases of designing and
building a suborbital rocket payload to do
astrophysics
• Science is realized when optics can direct
photons to detectors about 3 meters away.
• An optical bench separates the optics and the
detectors…
– Can we measure the relative alignment of these?
• Tip/Tilt and X/Y offsets
XACT Payload and Rocket
Nose Cone &
Recovery System
X-ray
Polarimeters,
Electronics, &
MXS
Telemetry and ACS
Systems
Aft Cone
& Door
Optical Bench
Black Brant VC
Terrier Mk70
A 1st approximation of complete XACT rocket
X-ray
Concentrators
& Star Tracker
Overall Payload Length: 3.26 m
Payload Diameter: 52 cm*
Payload Mass: 80.2 kg (include ST)
Alignment
• X-ray optics must not
shift laterally more
than ~1 mm from a
line connecting the
source to the detector
– Measure to 0.1 mm
• Optics must not tilt
relative to detector
more than ~ 2
arcminutes
– Measure to 1/5
arcminute
Laser
Position
Sensitive
Photodiodes
BeamSplitters
Laser
Position
Sensitive
Photodiodes
Lateral Shift Part
BeamSplitters
Tilt Part
Components
• Position Sensitive Photodiodes
– Produces analog voltage proportional to position
of light centroid
– Made by Pacific Silicon Sensor
•
•
•
•
Laser
Mirrors
Beamsplitters
“the Smarts”
– Combines the outputs of the photodiodes and puts
out 4 types of data: X and Y offset, Tip and Tilt
angle
I’ll give you
these as well
as a laser
and some
optics…
QuickTime™ and a
decompressor
are needed to see this picture.
Olin Student Job for XACT
Alignment System
• Design full system- including the
“smarts”
• Build a prototype system using two
optical benches separated by ~ 3
meters
• Test
• Document
Olin student Project #4: UV
flux monitor
• Our new modulated X-ray source uses UV
light to generate photoelectrons which are
accelerated into high voltage targets to make
X-rays
• We like to have absolute control of the X-ray
flux, which is driven by absolute control of the
UV light (from LEDs)
• We have found some evidence of UV LED
instability
• Need a way to monitor UV flux and record it
on a computer with time stamps.
The World’s First Fully
Controllable Modulated
X-ray Source
LED: Modulate This to
modulate the x-rays.
Optical
Photons
X-ray Photons
Vacuum Flange
Photoelectrons
Electron Target
Photocathode
•Characteristics:
• Rugged- no moving parts or fragile
filaments- perfect for space flight.
• Modulates x-rays at same rate that one
can modulate an LED
• Major NASA Uses:
•Timing Calibration
•A “flagged” in-flight Gain Calibration
Source: Have calibration photons only
when you want them and increase your
sensitivity by reducing the background
associated with the calibration photons
10 keV or more
Unpolarized MXS Prototype for XACT
HV FEEDTHROUGH
QUARTZ
WINDOWS (2)
BE WINDOW
UV
LEDs
QuickTime™ and a
decompressor
are needed to see this picture.
~3 days
Computer
which reads
and records
data at regular
intervals, or at
times when
there is a
change.
USB
Electronics
with a UV
photodiode
(Mouser has
several) and
circuit to read
it.
Objectives for Olin Summer
UV Flux monitor Project 2009
• Design and build UV Photodiode circuit
• Build a USB interface
• Write software to record data- perhaps
triggered by changes in flux
• Calibrate
Olin student Project: $75
Diffraction-limited microscope
“Simple” Microscope
webcam
Protective tube
Single lens
Olin student Project: $75
Diffraction-limited microscope
“Compound” Microscope: 2 lenses
Webcam: pixel size will limit resolution
Add on another Single lens
And maybe a support tube
Olin student Project: $75
Diffraction-limited microscope
• Requirements
– Approximately 1 micron resolution (~ 2 !)
– Reasonable working distance (~ 10 mm)
– Built-in calibration capability?
Olin student Project: $75
Diffraction-limited microscope
• Tasks
– Figure out single lens focal length
– Work out required additional lens
– Figure best-possible resolution based on
number of pixels, diffraction, etc
– Prove it!
• http://en.wikipedia.org/wiki/1951_USAF_Resolution_Test_Chart
Olin student Project: $75
Diffraction-limited microscope
• Out of the box:
– Roughly 5 mils is easy
– 1.3 Mpixel is 640 x 480 color
• 640 x 480 x 4 = 1.3 Mpixels
• From picture
– guess 127 um is 1/10 x 480 = 48
pixels, or 2.6 pixels/micron (color)
Shim stock on edge
0.005” = 127 m
Olin Objectives for Microscope
Project:
• Design add on optic for current
microscope
• Build and Test
• Update software to transfer calibration
to images
Olin student Project: Bit Error
Rate (BER) Test System
• Idea: quantitatively measure the performance
of a comm link
• Concept: Go digital!
– Send a pattern out with the transmitter
– At the receiver, recover the pattern
• May be difficult to find if many errors
• Overall time shift not important
• May be inverted
– Count the errors
• Accumulate statistics on type of error, etc
Olin student Project: Bit Error
Rate (BER) Test System
Error types
Clock
Rx
Tx
1
Transmitter
0110010111
0
Noise
•
Concept: Go digital!

Receiver
– Count the errors
• Accumulate statistics on type of error
Clock
recovery
0
Error
Error
Noisy
Channel
– Send a pattern out with the transmitter
– At the receiver, recover the pattern
• May be difficult to find if many errors
• Overall time shift not important
• May be inverted
1
0110010101
Olin student Project: Bit Error
Rate (BER) Test System
Error types
Clock
Rx
Tx
1
Transmitter
0110010111
0
Noise
•
Concept: Go digital!

Receiver
– Count the errors
• Accumulate statistics on type of error
Clock
recovery
0
Error
Error
Noisy
Channel
– Send a pattern out with the transmitter
– At the receiver, recover the pattern
• May be difficult to find if many errors
• Overall time shift not important
• May be inverted
1
0110010101
Block Diagram
Computer with Olin Student
software that prepares the
test pattern for
transmission, issues
transmit command, and
compares received to
transmitted. Finally
produces a BER figure
USB
Olin Electronics
box that
produces test
pattern and
sends it out a
BNC. Box also
has a BNC for
the receive end
BNC
out
“comm Link”
BNC
In
Olin student Project: Bit Error
Rate (BER) Test System
• Tasks
– Choose test patterns, build generator
– Develop clock recovery (PLL)
– Develop “pattern recognition”
• Cross-correlation based often best
– Time shift by bits to find best fit
– Accumulate error statistics
– BER = number of errors/total bits sent
Projects we probably wont do
this year
“i-Heliograph”
• Can we make a low power data
transmitter to send “lots” of data from
the moon to the earth using a 19th
century idea enhanced with 21st
century technology?
• How does such a system compare to
laser communication?
QuickTime™ and a
decompressor
are needed to see this picture.
QuickTime™ and a
decompressor
are needed to see this picture.
Replace this guy with a
high speed optical
modulator and an
ethernet port.
Replace this guy with a
avalanche photodiode
and an ethernet port..
Replacing the guy wiggling the
mirror
• Voltage Controlled LCD displays (KHz
Speeds?)
• Acoustic Optical Modulators (speeds up
to 100 MHz)
Replacing the guy using his
eye to see the signal on the
receive end
• Avalanche Photo diodes
There should be a power
savings compared to Laser
Comm
• Lasers are ~10% efficient on producing
optical output from electricity it gathers
from ~25% efficient solar cells.
– Total efficiency from sun = 0.25 * 0.1 =
2.5%
• Mirrors are ~90% reflective
Other factors in comparison
• Mass to moon
– Do solar cells and power system with
Laser weigh more than a mirror and
heliostat?
• Reliability
– Solar panels, motors, AOMs…
– Is dust an issue?
2009 Olin Job
• Build a Heliostat to capture the sun
• Pipe the light from the Heliostat through
either an accoustic optical modulator or a
LCD retarder
• Build a simple pulse frequency modulator to
drive the AOM or LCD retarder
• Build a demodulator to read the output of an
APD
• Predict performance and compare to Laser
Comm.
GSFC will provide
• A telescope base to make a heliostat
• An AOM to modulate light
• A Circuit design to produce a FM Pulse
train
• A Telescope for the receive end
• An APD (maybe dual use the one for
the MCA project)
• The demodulator design.
Olin student Project: Laser
Ranging System
Lunar Laser Ranging
• First suggested by R. H. Dicke in
early 1950s.
Background
•
MIT and soviet Union bounced laser
light off lunar surface in 1960s.
•
Retroreflectors proposed for Surveyor
missions but not flown.
•
Retroreflectors flown on 3 Apollo
missions.
Science of LLR
• Lunar ephemerides are a product of the LLR analysis
used by current and future spacecraft missions.
–
Lunar ranging has greatly improved knowledge of the Moon's orbit, enough to permit
accurate analyses of solar eclipses as far back as 1400 B.C.
• Gravitational physics:
–
–
–
–
Tests of the Equivalence principle
Accurate determination of the PPN parameter β,γ,
Limits on the time variation of the gravitational constant G,
Relativistic precession of lunar orbit (geodetic precession).
• Lunar Science:
–
–
Lunar tides
Interior structure (fluid core)
Optical Communications
• With an optical link it is
natural to use it for
communications in addition to
ranging.
• Potentially higher capacity
over large distances than RF
communications.
• Several methods currently
under development at GSFC.
Parameter
Wavelength (µm)
Data Rate (Mbps)
Tx aperture (cm)
Rx aperture (cm)
Code Rate
receiver sensitivity
(photons/bit)
BER
Output power (W)
Transmitter losses
(dB)
Net prop loss (dB)
Receiver losses
(dB)
Net Rx power (dBm)
Net Margin (dB)
Downli
nk
1.55
900
5.00
202.50
0.80
Upli
nk
0.775
550
40.00
5.00
0.80
100
100
1.50E1.50E-03
03
1
8
-3.8
-3.8
-80.78 -88.85
2
2
-52.58 -51.62
0.86 0.95
Other applications
• Collision avoidance
• Robotics
• Delay estimation
Olin student Project: Ranging System
Clock
Rx
Tx
1
Transmitter
0110010111
0
Noise
Concept: Nominally same as for BER
– Send a pattern out with the transmitter
– At the receiver, recover the pattern
• May be difficult to find if many errors
• BUT - Overall time shift IS important
• May be inverted
– Count the errors
• Accumulate statistics on type of error
Clock
recovery
0
Error
Error

Receiver
•
1
0110010101
Olin student Project: Ranging System
• Tasks
– Choose test patterns, build generator
– Develop clock recovery (PLL)
– Develop “pattern recognition”
• Cross-correlation based often best
– Time shift by bits to find best fit
– Measure time shift to get range