Pulsar Detection 2004 A Progress Report
By
James Van Prooyen N8PQK
SARA 2004
Annual Meeting
Development
and testing of Version 21 of the pulsar detector is complete.
This version
is an update with a new pulsar catalog and improved error reporting and logging.
This is the first released version for other to use.
Version 21
of the program continues to use the Radio Astronomy Supplies (RAS)
406.7 MHz
system and it associated software. Other
Radio Telescope receiver/computer may be used as long as the output file format
is compatible with the input file format of the Pulsar Detector. See the section
titled “File Formats” form more information.
A minor
modification of RAS data collection program is needed to run this program. See
the section titled “RA Modifications” for more information.
Work in
several different areas is being done to improve this system, …
The
pulsar detector works in the following manner. The signal is sampled using
a
time base that is some integral fraction of the period of the pulsar. Each
sample
taken during the duration of a single pulse period is assigned to a bin. The
sample can then be folded back so that samples from corresponding bins
are
added together. Each time we add a new series of bin values for the ongoing
totals, we "renormalize" by subtracting an amount from all of the bins
so
that
the weakest bin value is brought back to zero. Random noise in each bin tends to
average out and bins, which have a slightly higher average, will gradually
"grow" above the others. A picture then emerges which shows how the
average strength of the pulsar signal varies over it's period.
A filter
based on the pulsar period is then used for final processing of the data.
data is sent
to a file, the file name is selected from the catalog based on its index in the
catalog.
xxx
Data Files are named in the following format
DMMDDYYX.1 to DMMDDYYX.99
Where:
D stands for Data
MM is the current month from 01 to 12.
DD is the current day of the month from 01 to 31.
YY is the year from 00 to 99
X is a letter from A through Z, the first observation of the date
Would be “A” the second would be “B” and so forth through
“Z”.
The numbers 1 through 99 are the observation sequence IDs.
Listed below are example file names:
D063004A.1
This is a data file for 30 June 2004, it is the
first set of observations for the data listed.
D010100Z.99 This
data file is for 1 January 2000, it is the
last observation file for the day.
Pulsar
command files “RA_PSR21.CMD”, this file is used for input to the pulsar
processor, it is a set of commands for the processing of a data file set.
RA_PSR21.CAT
RA_PSR21.SET
The
program RA.EXE needs to be modified to work with the pulsar detector. An
additional time parameter to the data file header, this is the “seconds past
midnight” it is used by the pulsar detector to adjust the location of each
input data set in the internal arrays. With out this fix we get output that
looks like a saw tooth wave form. The source code for this in Turbo Basic is as
follows:
It
replaces the following code:
xxxxxxxxxxxxxxxxxxxx
The only
difference is an additional parameter in each data file to record the seconds
past midnight.
This
accuracy is needed for processing the data in the detection system.
The named
scan function is used to record the name of the pulsar that will be observed.
The data collection rate (know as DT) is set to "0.1" seconds.
After data
collection is complete the data is passed to the pulsar processor
(RA_PSR2).
The input
files to the pulsar detector can have any name but must be in the
format used
by the RAS receiver. The format is as follows:
"Pulsar J Name","Date/Time",Seconds Past Midnight, DT
0,Voltage
2,Voltage
N,Voltage
360,Voltage
Please note
the addition of "Seconds Past Midnight", this is used to fix data
collection timing problems that existed in version "1" of the pulsar
detector.
A modified
version of RAS's program "RA.EXE" was created called
"RA_21.EXE" and it has the above listed changes.
The pulsar
detection system is made up of several different files
RA_PSR2.BAS
Source code file for the pulsar detector
RA_PSR2.EXE
Executable program
RA_PSR2.CAT
The catalog of 1300 know pulsars
RA_PSR2.CMD
The command file, this has information on the
data files to be processed.
RA_PSR2.SET
Setup data
The output
file has arrays of data for plotting in Excel. Currently there are 4 different
data arrays saved for plotting, they are as follows:
|
Array Name |
Use |
|
Raw
Totaled Bin's |
Raw data |
|
Time
Corrected Bin's |
Used to
check processing |
|
Processed
Bin's |
The bin
after summing and normalization |
|
Filtered
Bin's |
The final
product of the processing several
are included in this report |
Example data
file which are plotted in this report are:
PSR76.DAT
PSR269.DAT
PSR1117.DAT
PSR1133.DAT
PSR1161.DAT
Please note
that the internal catalog name is used, many older operating systems will not
support the naming standard currently in use for naming pulsars.
The
following known bugs have been fixed in this version of the pulsar detection
system.
1. Data
collection timing. This was fixed by adding a parameter to the output file
that records the number of seconds past midnight when data collection
stared
for this record.
2. User
interface to complex, this was fixed be using a command file and
removing the user interface.
The
following are known bugs that have not been fixed.
a.
Dispersion, due to the fact that the RAS receiver has a band width of
only
75 KHz, and this version of the detector uses fixed bin's (0.1 second in
width),
dispersion corrections would have had little value, when most pulsars
that
have a dispersion of less
the 1000. Wider bandwidth receivers will need to
have adjustments for dispersion. The pulsar catalog does have
the dispersion
value for each pulsar.
b. Allow
batch processing of data.
c. Add
additional filters
d. Add
additional processing to allow the system to look into each data file to see
if it adds value to the data being processed.
e. Fix minor
plotting problems by adding a user selectable plot filter to the
program.
The
following are data plots from several different pulsars.
Pulsar
Name(s):
J1136+1551
B1133+16
RA_PSR2 Index:
269
Period:
1.1187913066 seconds
Dispersion:
4.864
Raw Data Files:
D062403A.1 through D062403A.99
Processed File:
PSR269.DAT
Run History:
C01
Notes:
Processing completed with no problems.
Data collected on June 24, 2003 between
1836 hours EST and 1944 hours EST.
Pulsar
Name(s):
J0452-1759
B0450-18
RA_PSR2 Index:
76
Period:
0.548939223 seconds
Dispersion:
39.903
Raw Data Files:
D071903B.1 through D071903B.99
Processed File:
PSR76.DAT
Run History:
C05
Notes:
Processing completed with no problems
Data collected on July 19, 2003 between
1010 hours EST and 1125 hours EST.
Automated collection.
Pulsar
Name(s):
J1915+1606
B1913+16
RA_PSR2 Index:
1117
Period:
0.059029998
Dispersion:
168.77
Raw Data Files:
D071603A.1 through D062403A.42
Processed File:
RPS1117.DAT
Run History:
C02
Notes:
Processing completed, pulsar period is outside
of the processing limits of this version of the
pulsar
detector.
Data collected on July 16, 2003 between
0051 hours EST and 0125 hours EST.
Pulsar
Name(s):
J1921+1419
B1919+14
RA_PSR2 Index:
1133
Period:
0.618182591
Dispersion:
91.64
Raw Data Files:
D071603B.1 through D071603B.42
Processed File:
PSR1133.DAT
Run History:
C03
Notes:
Processing completed with no problems.
Data collected on July 16, 2003 between
0051 hours EST and 0125 hours EST.
Pulsar
Name(s):
J1935+1616
B1933+16
RA_PSR2 Index:
1161
Period:
0.358738411
Dispersion:
158.521
Raw Data Files:
D071903A.1 through D071903A.99
Processed File:
PSR1133.DAT
Run History:
C04
Notes:
Processing completed with no problems.
Data collected on July 19, 2003 between
0100 hours EST and 0205 hours EST.
Data files D071903A.1 through D071903A.7
have zeros due to the
receiver-offset error.
This data set should be reprocessed with out
the first 7 files.
Development
of the pulsar detection system will continue with version RA_RSP21, which will
fix most of the known bugs identified in this report. Development will then
continue with an effort to recover the full pulsar wave
form using
the current RAS 406 MHz system.
We are also
working with RAS on a possible development of a hardware/software solution to
pulsar detection.