Using the GAVRT Radio Telescope: The SETI Project Lesson 3: Interpreting a Waterfall Plot Questions? Please contact Carolyn Donelan @ carolyn.donelan@richlandone.org.

What is a waterfall plot? A waterfall plot is an x-y plot with frequency of light plotted on the x- axis and time plotted on the y-axis. from: http://galileo.gavrt.org/seti/docs/GAVRT-SETI_Waterfall-1_v0.1.pdf

Interpreting a Waterfall Plot You need to be able to look at a waterfall plot and interpret what it means. In this activity, you will be given several possible explanations for a waterfall plot. You need to choose which explanation is the best explanation for each plot. Write down the Plot (letter) and Explanation (number), so you can see if your interpretations were correct.

Possible Explanations Just an overview of the entire data set. Two examples of obvious Radio Frequency Interference. Both signals last much too long to be valid, since the radio telescope would sweep across a real source in just a few seconds. Some noise, which is spread out over too many frequencies to be a real signal. Near the noise is a possible candidate, but it’s a judgment call, because it could be associated with the noise. (Dr. Levin suggests keeping it as a possible candidate.) Shows a SETI candidate, worthy of follow-up to see if it shows up again at the same time and frequency when this patch of sky is next observed. Shows the same SETI candidate, but with the frequency, time, and color all zoomed in to examine it more closely. If it showed up as 2 or 3 dots when we do this, that would be exciting, because a real signal would show up for a second or two as the telescope sweeps across it. Nonetheless, this image is pretty bright and is not obviously RFI or noise, so we add it to the list of candidates. 1=E, 2=D, 3=C, 4=A, 5=B

The next slide has all possible explanations, so you can go back and forth, to view the plot and the explanations. Waterfall Plot A from: http://galileo.gavrt.org/seti/docs/GAVRT-SETI_Waterfall-2_v0.1.pdf

Possible Explanations Just an overview of the entire data set. Two examples of obvious Radio Frequency Interference. Both signals last much too long to be valid, since the radio telescope would sweep across a real source in just a few seconds. Some noise, which is spread out over too many frequencies to be a real signal. Near the noise is a possible candidate, but it’s a judgment call, because it could be associated with the noise. (Dr. Levin suggests keeping it as a possible candidate.) Shows a SETI candidate, worthy of follow-up to see if it shows up again at the same time and frequency when this patch of sky is next observed. Shows the same SETI candidate, but with the frequency, time, and color all zoomed in to examine it more closely. If it showed up as 2 or 3 dots when we do this, that would be exciting, because a real signal would show up for a second or two as the telescope sweeps across it. Nonetheless, this image is pretty bright and is not obviously RFI or noise, so we add it to the list of candidates. 1=E, 2=D, 3=C, 4=A, 5=B

The next slide has all possible explanations, so you can go back and forth, to view the plot and the explanations. Waterfall Plot B from: http://galileo.gavrt.org/seti/docs/GAVRT-SETI_Waterfall-2_v0.1.pdf

Possible Explanations Just an overview of the entire data set. Two examples of obvious Radio Frequency Interference. Both signals last much too long to be valid, since the radio telescope would sweep across a real source in just a few seconds. Some noise, which is spread out over too many frequencies to be a real signal. Near the noise is a possible candidate, but it’s a judgment call, because it could be associated with the noise. (Dr. Levin suggests keeping it as a possible candidate.) Shows a SETI candidate, worthy of follow-up to see if it shows up again at the same time and frequency when this patch of sky is next observed. Shows the same SETI candidate, but with the frequency, time, and color all zoomed in to examine it more closely. If it showed up as 2 or 3 dots when we do this, that would be exciting, because a real signal would show up for a second or two as the telescope sweeps across it. Nonetheless, this image is pretty bright and is not obviously RFI or noise, so we add it to the list of candidates. 1=E, 2=D, 3=C, 4=A, 5=B

The next slide has all possible explanations, so you can go back and forth, to view the plot and the explanations. Waterfall Plot C from: http://galileo.gavrt.org/seti/docs/GAVRT-SETI_Waterfall-2_v0.1.pdf

Possible Explanations Just an overview of the entire data set. Two examples of obvious Radio Frequency Interference. Both signals last much too long to be valid, since the radio telescope would sweep across a real source in just a few seconds. Some noise, which is spread out over too many frequencies to be a real signal. Near the noise is a possible candidate, but it’s a judgment call, because it could be associated with the noise. (Dr. Levin suggests keeping it as a possible candidate.) Shows a SETI candidate, worthy of follow-up to see if it shows up again at the same time and frequency when this patch of sky is next observed. Shows the same SETI candidate, but with the frequency, time, and color all zoomed in to examine it more closely. If it showed up as 2 or 3 dots when we do this, that would be exciting, because a real signal would show up for a second or two as the telescope sweeps across it. Nonetheless, this image is pretty bright and is not obviously RFI or noise, so we add it to the list of candidates. 1=E, 2=D, 3=C, 4=A, 5=B

The next slide has all possible explanations, so you can go back and forth, to view the plot and the explanations. Waterfall Plot D from: http://galileo.gavrt.org/seti/docs/GAVRT-SETI_Waterfall-2_v0.1.pdf

Possible Explanations Just an overview of the entire data set. Two examples of obvious Radio Frequency Interference. Both signals last much too long to be valid, since the radio telescope would sweep across a real source in just a few seconds. Some noise, which is spread out over too many frequencies to be a real signal. Near the noise is a possible candidate, but it’s a judgment call, because it could be associated with the noise. (Dr. Levin suggests keeping it as a possible candidate.) Shows a SETI candidate, worthy of follow-up to see if it shows up again at the same time and frequency when this patch of sky is next observed. Shows the same SETI candidate, but with the frequency, time, and color all zoomed in to examine it more closely. If it showed up as 2 or 3 dots when we do this, that would be exciting, because a real signal would show up for a second or two as the telescope sweeps across it. Nonetheless, this image is pretty bright and is not obviously RFI or noise, so we add it to the list of candidates. 1=E, 2=D, 3=C, 4=A, 5=B

The next slide has all possible explanations, so you can go back and forth, to view the plot and the explanations. Waterfall Plot E from: http://galileo.gavrt.org/seti/docs/GAVRT-SETI_Waterfall-2_v0.1.pdf

Possible Explanations Just an overview of the entire data set. Two examples of obvious Radio Frequency Interference. Both signals last much too long to be valid, since the radio telescope would sweep across a real source in just a few seconds. Some noise, which is spread out over too many frequencies to be a real signal. Near the noise is a possible candidate, but it’s a judgment call, because it could be associated with the noise. (Dr. Levin suggests keeping it as a possible candidate.) Shows a SETI candidate, worthy of follow-up to see if it shows up again at the same time and frequency when this patch of sky is next observed. Shows the same SETI candidate, but with the frequency, time, and color all zoomed in to examine it more closely. If it showed up as 2 or 3 dots when we do this, that would be exciting, because a real signal would show up for a second or two as the telescope sweeps across it. Nonetheless, this image is pretty bright and is not obviously RFI or noise, so we add it to the list of candidates. 1=E, 2=D, 3=C, 4=A, 5=B

Answers are on the next slide! Don’t look at the answers until you have written down the plot (letter) and explanation (number) for each slide!

Answers! Plot A is explanation 4 Plot B is explanation 5 Plot C is explanation 3 Plot D is explanation 2 Plot E is explanation 1