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Pulsar Detection Progress Report 2003
by James Van Prooyen N8PQK
| Society of Amateur Radio Astronomers
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Development and testing of Version 2 of the pulsar detector is nearly complete. Version 2 is a complete rewrite of the detection system with a number of bugs fixed and several new features added to the system.
Overview
Version 2 of the program continues to use the Radio Astronomy Supplies (RAS) 406.7 MHz system and it associated software. 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).
Input Files
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.
Processing File
The pulsar detection system is made up of several different files:
Output Files
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 Bins | Raw data |
| Time Corrected Bins | Used to check processing |
| Processed Bins | The bin after summing and normalization |
| Filtered Bins | The final product of the processing several are included in this report |
Click on the above data file names to see the respective plots.
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.
Processing
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 are sent to a file, the file name is selected from the catalog based on its index in the catalog.
Bugs Fixed
The following known bugs have been fixed in this version of the pulsar detection system.
Bugs Not Fixed
The following are known bugs that have not been fixed.
Data
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 without the first 7 files.
Plans
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.
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