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Using a World-Class Telescope to Spy on Venus

Posted on Thu, May 4, 2017
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In late March, I traveled to Puerto Rico to conduct observations of Venus using the Arecibo Observatory telescope. It was the second time I traveled to the observatory to make radar measurements of the surface of Venus. Even though it was my second time there, the size and capability of the telescope still impressed me.

A number of computer screens in front of a large window.

View of the telescope platform from the window in the control room. The platform spins in order to track Venus as it moves across the sky. Image: Jennifer Whitten

The Arecibo Observatory is used by scientists around the world for studying a variety of topics, from Earth’s ionosphere, to asteroids and planetary bodies, to pulsars and galaxies. Scientists here at the National Air and Space Museum’s Center for Earth and Planetary Studies (CEPS) have recently used Arecibo to study the Moon and Venus. Observations of the Moon take place over the course of a couple of days, but for Venus we usually observe for 10 days. We can observe the Moon for most of the year because it’s always pretty close to Earth. But Venus is closest to Earth (in inferior conjunction) for only a short period of time. During the rest of the year, Venus is too far away from Earth to make the high resolution measurements we need.

This time around, I split the 10-day observation period with another CEPS researcher, Gareth Morgan. Gareth took the first half of the week and I took the second half. Observations of Venus typically last 2.5 hours when Venus is within the field of view of the Arecibo telescope. We are assigned an approximately 4-hour block of time each day to work with the telescope because  we need the extra time to set up the telescope for our observations. We have to plug many different cables into racks in the control room to ensure that the signal we are receiving from Venus is being filtered and amplified properly.

Woman stands in front of a large control board with multiple wires and access points.

Plugging in the cables to set up the signal processing for our observations of Venus. Image: Jennifer Whitten

In addition to plugging in cables for the signal processing, we also need to send certain commands to the telescope to get it ready to observe Venus. There is a computer station set up in the control room where the observer (that’s me!) can control the telescope. I enter many different computer commands to set up the software to record the data collected from the surface of Venus. Each day I create an empty document labeled with the date for the computer to store the data. Then I send commands to the telescope to get it ready to observe Venus. One computer command ensures that the telescope is ready to transmit the radio waves to Venus, and another tells the telescope where to point in the sky to view Venus as soon as it enters the telescope’s field of view. Once the planet comes into view, we send a command telling the telescope to start transmitting a signal.

Woman enters in commands into a computer while a man looks on.

The telescope operator waits for me to finish typing in all the computer commands to get the telescope ready so he can start to warm up the transmitter. Image: Jennifer Whitten

I need help running the telescope, so every observation day there was a telescope operator in the control room getting the telescope transmitter ready. The telescope operator is in charge of making sure that the telescope transmitter outputs a steady amount of power throughout the entire 2.5-hour observation period.

Man works at a small desk surrounded by equipment.

This is Israel Cabrera, one of the telescope operators that worked with me this year. He is sitting in front of the transmitter computer monitor, checking many different measurements to ensure that the telescope is running smoothly. Image: Jennifer Whitten

It takes about 5 minutes for the radio wave to travel to Venus, bounce off the surface, and return to the Arecibo telescope dish. Generally, we transmit radio waves to Venus for 5 minutes and then receive for 5 minutes. We can see the returned signal in real time on one of the monitors in the control room.

Graph with a yellow line spiking at the center of the chart.

The yellow line is the returned radio signal from Venus. The height of the peak indicates the strength of the signal bouncing off the planet’s surface (the higher the better) and the squiggles in the yellow line are different surface features on Venus. Image: Jennifer Whitten

We can take this returned signal and turn it into beautiful and scientifically useful data products for analysis. For these data, we are particularly interested in analyzing the lava flows and the impact crater ejecta. By looking at lava flows and impact craters we can start to study the recent volcanic history on Venus. For instance, we still aren’t sure if Venus is volcanically active today! We can use these radar data to study recent volcanic activity and search for evidence of ongoing volcanic activity. The research is ongoing and the data we collected from this trip will be vital to our understanding of the planet.

Black and white image of half of Venus with arrows pointing to different features.

A 12.6-centimeter wavelength radar image of the southern hemisphere of Venus collected at the Arecibo Observatory in March 2017. This view of Venus shows craters (yellow), corona (blue), and lava flows (red). Image: Smithsonian Institution/NASA GFSC/Arecibo Observatory/NAIC

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