Notes to myself
Notes to refresh what's left of my memory
(or: "an attempt to postpone the losing battle with entropy").
continuous to discrete fourier transform
after convolving 2 gaussians.
acf-> spectra memo (.pdf)
rms voltages needed for
2,3,4, and 5 bit sampling.
clipping a sine
(how strong the various freq terms are)
Harmonics created when clipping a
Side band harmonics do not
always move farther out than at the fundamental.
a 90 deg hybrid to convert linear to circular (lbw example)
properities of a gaussian
properteis of sin(x)/x
idl to process ao spectral line data
satellite orbits: velocity,angular
velocity, period vs radius
sun,moon separation during 21aug17 eclipse
of cpu compute servers at AO.
locations by cpu
up of monitor data.
format. converting big endian to little endian.
- side band harmonics do
not always move farther out than at the fundamental. (top)
Suppose you have a tone of Amplitude A and
frequency w and a side band of amplitude B and frequency
(Aexp(iwt)+Bexp(i(w+delta)*t)2= AAexp(i2wt)+ ABexp(i(2wt
+delta)) + BB*exp(i(2w+2delta)t)
If B << A then the AB term will be much larger than the BB
term so the +delta signal will be stronger than the 2*delta.
- Gaussian: (top)
A gaussian centered at x=0 can be defined as:
integral normalized to unity
|integral -inf to inf
|FWHM=m*sig (see 1*)
- sin(x)/x (top)
y=sin(x)/x . If x is defined in units of the first null, then use
|maxvalue : y(0)
||when x=tan(x) (more
for large x :close to x=(2n+1)pi/2
|x when y=.5
|integral between 1st
voltage levels for 2, 3, , and 5 bit sampling were computed using
the threshold levels from fred schwab. To compute the rmsVolts I
just took PktoPkVolts/Nlevels * sigmaLevels. This ignores the
problem of whether or not the levels are centered on 0 volts or not.
rms voltages needed
for 2,3,4, and 5 bit sampling. (top)
Rms Volts vs Nbits
|rms (Volts) assuming
2V PkToPk A/D
|rms (Volts) Assuming
5V PkToPk A/D (ri)
The receiver temperature is computed using a hot
and cold load at the input. let:
If we measure the output power ratio on load1 and load2:
- T1 and T2 be the temperatures of these loads.
- gamma is the voltage reflection at the input to the horn. let
G2=(1-gamma^2). It will be the fraction of the input power that
gets into the device
- alpha is the loss in the omt, Tomt is the temperature of the
omt. (1-alpha) of the entering temp will be passed through.
(1-alpha)*Tomt will be contributed by the omt temp.
- Tamp is the amplifier temperature. Trcv is normally Tamp
Solving for Tamp gives:
y=(Tamp + alpha*Tomt + (1-gamma^2)(1-alfa)T2)/(Tamp + alpha*Tomt + (1-gamma^2)(1-alpha)T1)
If you assume that alpha,gamma are equal to zero, then you will get
a Tamp that is higher than it really is.
Tamp(1-Y)=Y(alpha*Tomt + (1-alpha)(1-gamma^2)*T1) - (alpha*Tomt + (1-alpha)(1-gamma^2)T2)
Tamp= (1-alpha)(1-gamma^2)*(T2-Y*T1)/(Y-1) - alpha*Tomt
- Ae= effective area (aperture). (PowerExtracted/IncidentFlux)
- nA=aperture efficiency ( Ae/Ag) Ag=geometric aperture)
- D=Gmax=4piAe/(lamda^2) or
- Ae*bmSa = lamda^2 (bmSa=beam solid angle)
k - boltzman's constant
K - deg Kelvin
Jy - Jansky
m - meters
w = watts
J - Joules
Ae - effective area of telescope
G - gain
T - Tsys
|k: Boltsmans' Constant
|convert TempK to energy
|flux density per hz
|1380 (m^2/K) for 1 Jy
2760 (m^2/K) for 1 Jy single pol?
|A telescope with Ae=2760 m^2
Ae/2760 = 1K for a 1 Jy source
|Gain 1K/Jy = 2760m^2
|G = K/Jy = Ae/2760.
|G/T = (Ae/T)/2760.
|SEFD=T/G = (T/Ae) * 2760.
sefd vs T/Ae (.ps) (.pdf)
Brightnes and Flux density
- 1 K/Jy is 2760 m^2
- for a uniformilly illuminated circular appeture:
- if plane wave with energy power density S hit telescope. The
telescope extracts Pe energy then the effective area of the
telescope is Ae=Pe/S
- The appeture efficiency is Na=Ae/Ag where Ag is the
- Ae*OmegaA=lambda^2 where OmegaA is the beam solid angle
(integrated over 4pi steradian).
- OmegaMb is the main beam solid angle. Defined to be the solid
angle that has the same area as the mainbeam down to the first
- dm smearing across a band
- tmSmMillisecs= (202/cfrMhz)^3 * dm *BwMhz
- optimum channel width for incoherent processing
- 1/channelwidth = dmsmearing across the channel..
- 1./(bw/nchan) = dmSmearingbw/nchan
- nchan/dmSmearingBw = bw/nchan
- nchan= sqrt(bw*dmSmearingBw) optimum.. or
- nchan=sqrt(bwMHz^2 * (202/cfrMhz)^3 * dm * 1e3)
The plots show satellite
orbital velocities, angular velocity, and orbital periods vs
radius (.ps) (.pdf)
- Page 1: orbits vs radius from center of earth
- top: velocity km/sec
- 2nd: velocity km/hour
- 3rd: obital angular velocity
- 4th orbital period in hours
- Page 2: orbits versus distance above the earth
- Page 3: blowup showing 0.. 1000 km above the earth's surface.
- The dashed red lines shows the geostationary orbit.
- Page 4: How long a satellite is above the observers horizon
(assuming sea level, min elevation=0)
- Page 5: How fast does a telescope need to move to track
satellites at various heights..
- red lines show the 12meter limit (50 km?) and the 305 m
limit (6000 km).
- The lines are the max velocities.. you probably can't track
continually at this speed (you always need a little extra if
you ever need to catch up..).
170821 sun moon separation as see from AO
I plotted up the sun,moon separation for the
21aug17 eclipse (as seen from arecibo observatory).
I used the jpl horizons ephemerides to compute the separation.
the plot shows
the sun moon separation (.ps) (.pdf)
- the moon, sun edges will start to intersect at 14:18 ast
- the minimum distance (maximum for eclipse) will occur at 15:34:00.3
- the minimum separation (of their centers) will be .099
degrees (about 6 arc minutes).
- the moon , sun will finish their overlap at 16:40
- How directories are used:
- main developement goes on here
- Different versions stores with possible updates needed to
fix a version
- snapshots of a particular version. It is frozen. Might be
easier to role back
- V3.0.10 (normal)
- V3.1.03 (smart)
- idl - holds phil's idl code
- idl directories under /pkg/rsi/local/libao/phil
- pdev - the datataking system for pdev. excludes jeff's code
- rev-1026/ before parallactic angle changes 16feb09
- rev-879/ before psrfits changes.
- vw - vxWorks datataking code from /home/phil/vw/
- directory under /home/phil/vw/
- vwTcl - tcl procedures for vxWorks. from /home/online/vw/Tcl
- code from /home/online/vw/Tcl
- list contents of repository:
- svn list file:///share/megs/phil/svnrepos
- copy a new set of files into the repository
svn notes CIMA
- file:///share/megs/phil/svnrepos/Cima ..
- Online cima versions:
- /home/cima/Software/XX XX= Mocksp, Svnwork
- Working directories
- /home/cima/svn/Cima/XX XX =
- svn list file:///share/megs/phil/svnrepos/Cima
- checkout to a working directory
- cd /home/cima/svn/Cima/ ; mkdir mocksp
- svn -r revision checkout
- Make Svnwork a new cima version release (eg. Mocksp)
- make sure svn repository uptodate for svn/Cima/svnwork svn
- record svn version number
- cd /home/cima/svn/Cima/svnwork
- make install
- moves most recent updates to Svnwork
- does a cmake install aon Frontend,Exectuive,
tcl_utilities, then copies the version files back to
- add /home/cima/bin to front of path variable (to find cmake)
- Copy online version Svnwork to new version
- cima_copy Svnwork Mocksp
- answer Questions: mocksp 3.2.00
- Make a branch for a new version in the svn repository.
- svn copy file:///share/megs/phil/svnrepos/Cima/trunk
"creating mocksp branch from trunk revision (revision
number from status above)"
- checkout the mocksp version
- cd /home/cima/svn/
- svn checkout
SVN notes pdev