1. Using the GAVRT Radio Telescope: The SETI Project
Lesson 7: Analyzing a Scan
Questions? Please contact Carolyn

2. FOR TEACHERS!!! It takes approximately 40 minutes to complete a scan.
GAVRT Live Video Feed is available here: Feeds/DSS28-Video/index.php (You can see the telescope moving as it takes your class’ scan!)
While the telescope is completing the scan, students can either analyze the data as it is received, or they can analyze a previous scan.

3. FOR TEACHERS!!!
If you choose to analyze a previous scan, look at previously submitted scans here:
GAVRT SETI hopes to find a candidate with repeated observations in the same skyframe. So, find a skyframe with some potential candidates and see if a new scan is available in the datasource menu.

4. Analyzing your Scan
A message from Dr. Levin: “This is the real heart of what the students are doing. In many ways, they are doing this analysis because it is too hard for a computer to do. People do a great job at recognizing patterns. Computers generally need to be told what sort of pattern to look for, and they are very literal about it. So when you add a little noise to the RFI signal, and let it wander in frequency a bit, with perhaps some starts and stops or changes in power level, it gets hard to write a computer program which will still recognize it as RFI. A human being has no such problem. Most of us can glance at a plot, see the vertical lines in the data, and immediately recognize the difference between a long line and a short one.”

5. Analyzing your Scan
Go to
Near the bottom of the screen, use “Data Source” to choose your data file from the pull-down menu.
The first 8 characters in a datasource file name represent the skyframe being scanned. For example, spc00599_ _ and spc00599_ _ are two different scans of the same skyframe.
Complete the header section on the SETI_Spec_Data_Worksheet. (go to the next slide for more instructions)

6. Analyzing your Scan Mask any obvious RFIs.
Record the frequencies and times of the RFIs in Section A (Interference RFI data) on the SETI_Spec_Data_Worksheet. (go to the next slide for more instructions)

7. Analyzing your Scan
Are there other frequencies/times that could be noise or interference?
Record these frequencies/times in Section B (Possible Instrumental noise or Interference). (go to the next slide for more instructions)

8. Analyzing your Scan
Look at the remaining plot, with known RFI removed.
Make sure that Markers are checked “on”.
from:

9. Analyzing your Scan
Are there any bright signals left? Are there any that could be candidates?
a very short vertical line, lasting a few seconds, or
two or three short lines, separated by 360 seconds (the time it takes for the telescope to get to the adjacent scanline)
Record those in Section C (Candidates). (go to the next slide for more instructions)

10. Before Submitting your Scan
Double-check your Data Worksheet before submitting it to GAVRT.
The header section, at the top of the report, gives information about which skyframe was observed, when the data were collected, the datasource, and who did the observing. This is necessary in order to recognize which reports should be compared with each other, and is also useful if you have questions and need to contact the people who collected the data and wrote the report.
The Radio Frequency Interference (RFI) section gives information about interference signals which you have identified and removed. This lets you know in which channels we're "blind" (or can't trust what we see) because of RFI, and also allows for a better understanding of potential signals. For example, if you have what looks like a good candidate in a skyframe today, but it falls in a channel which contains RFI in most of the observations from other days (datasources for different skyframes), you might suspect that it too is RFI.
The Possible Noise or Interference section is for events which you really don't think are good candidates, but don't have sufficient evidence to be ruled out. Basically, this is where the weird-looking stuff goes, to encourage everyone to think about it, look for patterns, and try to figure out what's going on.
The Candidates section, of course, is where you put events which just might be radio signals from extraterrestrial intelligence. If they're brighter than the background noise, or they repeat with just the right timing to be coming from adjacent scan lines (remember the racetrack scan pattern), and you can't rule them out as RFI or an instrumental problem, then they get listed here.
Source:

11. Analyzing your Scan
11. More things to consider: