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My Solar-Called Life: Solar Week Scientist Blog

February 2007 - Posts

  • CHARM Payload Integration

    When we finished our initial calibrations of the bagels and top hats in November 2006, Scott Bounds and I took them out to the NASA Wallops Flight Facilty in Virginia for the payload integration and testing. During a rocket integration, the instruments built by the different groups involved with the rocket are put together on the payload for the very first time with the help of the NASA engineers and technicians. The picture below shows NASA engineer Shane Thompson working on the payload. I've marked some of the different instruments on the payload. The electric field booms and Langmuir probes are folded up and tied up with wires so they will fit inside the nose cone of the rocket. You can see 5 of the bagels I tested in the picture. Some of the scientists thought the metal piece to which the bagels are attached looked like a shamrock, so we called it our "Lucky CHARM." There are two bagels on each of the four leaves of the shamrock-shaped piece of metal.

    During integration, the electronics are tested and checked for problems on the payload. I wasn't able to stay at NASA Wallops for the entire integration, but I did get to see a sequence test, which is a sort of dress-rehearsal of the flight to make sure the systems that control the timing of various events during the flight are working properly. The NASA engineers and techinicians also perform tests on the payload to make sure it can withstand the vibrations during the flight and is balanced properly. The rocket payload will be spinning during the flight to help stabilize the rocket, so it is very important that the payload is properly balanced. The picture below shows Clay Merscham and Shane Thompson getting ready for the spin/balancing test. At NASA Wallops, they also perform a spin deployment test to make sure that the various instruments will deploy properly. During the flight, the rocket's nose cone will be ejected so the instruments can be deployed to take measurements. Instruments like the electric field booms and Langmuir probes are designed so that the spinning of the rocket will cause them to unfold. Our top hat deployer arms also will unfold and lock into place due to the spinning of the rocket. This video of the spin deployment test for the HIBAR rocket that Jim LaBelle launched a few years ago will show you what this test is like. The tests are very rigorous and it is common for things to get broken.

    The payload integration and testing was finished at the end of December 2006. After the integration, we only had a couple of weeks in January to fix the things that were broken during testing and peform the final calibrations on our bagel and top hat electron detectors. Then everything was shipped to the Poker Flat Research Range near Fairbanks, Alaska to prepare for the rocket launch.

  • The Rocket Launch!

    After months of hard work building and testing the instruments and a few weeks of waiting for just the right auroral conditions, the CHARM sounding rocket (also known as 40.019 UE Black Brant XII) was launched from the Poker Flat Research Range in Alaska on February 28, 2007 at 08:39:41 Z (that's 2:39:41 AM CST).

    I hope you enjoyed reading about the detector calibrations, integration and testing for the CHARM sounding rocket. If you'd like to read more about sounding rockets, Professor Kristina Lynch from Dartmouth College has an interesting online journal about the ROPA rocket that was launched from Poker Flat on February 12, 2007. I didn't get to travel to Alaska to watch the CHARM launch, so reading Professor Lynch's web page will give you a better idea of what happens out in the field while making the final preparations for the launch. You can also learn about all of the rockets that were launched from Poker Flat in 2007, as well as the upcoming sounding rocket missions on the NASA Sounding Rocket Program Office web site.

  • Testing the Detectors For CHARM

    Before our eight bagels and two top hats could be flown on the sounding rocket, we had to calibrate them. This can be time consuming, so Professor Kletzing asked me to help Scott Bounds, another University of Iowa scientist, with the tests. I had never done anything like this before, so I had to learn how the detectors work and how to use the test equipment in our laboratory.

    To calibrate the detectors, we put them into a big stainless steel vacuum chamber and pump out as much of the air as possible. This helps us simulate the conditions in space. Also, the microchannel plates in our detectors can be damaged if we power up the detectors at atmospheric pressure (760 Torr). To pump out our vacuum chamber we use two kinds of pumps. First, we use a mechanical pump to reduce the pressure in the chamber to about 1x10-3 Torr. Then we use a cryopump to reduce the pressure in the chamber even further to about 5x10-6 Torr (that's less than 1 millionth of atmospheric pressure). The difference between the air pressure inside and outside the vacuum chamber is so huge that it is impossible to open the vacuum chamber door when we are running the pumps. You would have to be as strong as Superman to open it! The pictures below shows me standing next to the vacuum chamber and the inside of the vacuum chamber with a detector that is ready to test.

    Inside the vacuum chamber, an ultraviolet lamp provides a source of electrons. We need to know how many electrons our source produces, so we use another type of electron detector, called a Faraday cup, that has already been calibrated. To test the detectors for CHARM, we put one of the bagels or top hats inside the vacuum chamber. The detector sits on a special table that allows us to change the detector orientation relative to the electron source. The detector electronics sit on a shelf inside the vacuum chamber and are connected to a computer outside the chamber that controls the test and records the data.

    It takes between 1 to 3 hours to pump the air out of the vacuum chamber. Once the air has been pumped out, it takes about 4 hours to test a bagel. The top hats take longer since we need to check many different detector orientations relative to the electron source. Fortunately, the tests are controlled by a computer, so we only need to check on the test once in a while to make sure everything is working. When a test is finished, we analyze the data files to make sure the calibration factors look okay. Sometimes the detectors didn't work properly, so we had to open up the vacuum chamber, fix any problems with the detector and electronics, and repeat the test. It was really frustrating when there were problems, but I sure learned a lot while helping Scott Bounds figure out what was wrong.

  • Building the Detectors For CHARM

    It takes a lot of different people to put together instruments for a sounding rocket. Here are a few of the people from the University of Iowa who helped get the bagel and top hat style electron detectors ready for the CHARM sounding rocket:

    Our undergraduate student, Kristin Wood, helped with the technical drawings and the top hat deployer arms.

     

    Mike Fountain from our machine shop made the parts for the detectors.

    Graduate student Mike Larson put a special black coating made from copper on the top hats.

     

    Our assembly technician, Sharon Kutcher, soldered all of the electronics.

  • Top Hats and Bagel Detectors for CHARM

    I bet you're wondering what an old-fashioned hat and a chewy breakfast roll have to do with space science! Top hats and bagels are two types of electrostatic analyzers flown on sounding rockets to measure high-energy electrons in space. Scientists from the University of Iowa built top hat and bagel electrostatic analyzers for the CHARM sounding rocket.

    The names of these two types of instruments come from the geometry of the detectors. The top hat (example shown below) consists of two metal hemispheres nested inside one another. The detector itself doesn't look much like a top hat. The name refers to the metal piece that sits on top of the two hemispheres like a "hat." When a voltage difference is applied between the two hemispheres, electrons entering the detector are deflected by the resulting electric field and follow a curved path. The amount of the deflection depends upon the detector voltage and the energies of the electrons, so only electrons with a selected range of velocities can enter the detector. By changing the voltage we can detect electrons with different velocities. Near the bottom of the detector are a pair of microchannel plates, which multiply the number of electrons to make the signal produced by the incoming electrons easier to measure. The CHARM rocket has two top hats that can measure the both the electron energies and the directions in which the electrons are traveling.

    The basic idea behind a bagel detector is similar to a top hat, but the bagel has a different geometry. If you take apart a bagel detector (shown below), you will see that the inside of the detector looks like half of a bagel. The bagel half nests inside a hollowed out half-bagel (sort of like a bagel's crust). When we put a voltage on the inner bagel, electrons follow a curved path up through the hole in the center of the bagel. The hole is covered by a pair of microchannel plates, which multiplies the number of electrons to make them easier to measure, just like in the top hat detector. The CHARM rocket has eight bagels. Each of the eight bagels measures electrons at a specific energy traveling along the Earth's magnetic field.

  • We're Rocket Scientists! (Kris Sigsbee)

    My supervisor, Professor Craig Kletzing, and Dr. Scott Bounds, another University of Iowa scientist, build instruments for NASA sounding rockets. In the fall of 2006, I had the opportunity to help them test instruments that will be flown on the “Correlations of High-Frequencies and Auroral Roar Measurements” (CHARM). I was very excited about working on this project. I've always wanted to be a rocket scientist!

    NASA sounding rockets carry scientific instruments into space to help scientists study the Sun, the Earth’s upper atmosphere, and the aurora borealis. The name “sounding rocket” comes from the nautical term “to sound,” which means “to measure.” In oceanography, sounding is a way to measure the depth of a body of water or to investigate the bottom of the sea using a weighted line. In the space and atmospheric sciences, we use sounding rockets to probe the upper atmosphere or space. A sounding rocket is launched into space on a parabolic trajectory, which means it goes up into space, makes measurements, and then falls back to the Earth. Sounding rockets are sub-orbital, so they do not go into orbit around the Earth, although they can reach altitudes higher than the orbit of the International Space Station (~390 km).

    Jim LaBelle from Dartmouth College is the principal investigator of the CHARM sounding rocket. The CHARM payload has instruments to measure electrons, electric fields, and magnetic fields that were designed to help us learn about high-frequency waves in the Earth’s aurora. Scientists from the University of Iowa built the electron detectors for CHARM. NASA uses many different types of sounding rockets to launch scientific instruments into space. The CHARM payload will be launched on board a type of sounding rocket called a Black Brant XII. The launch will take place in late February or March 2007 at the Poker Flat Research Range near Fairbanks, Alaska. On the launch schedule, our rocket is called LaBelle 40.019. CHARM is the last of 10 sounding rockets that will be launched from Poker Flat to study the northern lights during the winter of 2007.

  • A Typical Day in Van Allen Hall (Kris Sigsbee)

    I work in the Department of Physics and Astronomy at the University of Iowa, where I am part of the Experimental Particles and Electric Field Group. Scientists at the University of Iowa have been involved in many NASA space science missions, including Voyager 1 and 2, Galileo, Polar, Cluster, Mars Express, Cassini, and the upcoming Juno and Radiation Belt Storm Probes missions. The building in which I work is named after James Van Allen, who was probably the most famous space scientist to work at the University of Iowa. Dr. Van Allen built a scientific instrument for Explorer 1, the first U.S. satellite, and discovered the Van Allen Radiation Belts.

    During a typical day at work, I might write a computer program to analyze data from satellites making measurements in the Earth’s magnetosphere. Sometimes I use web sites on the Internet to plot and download satellite data. I often read papers in scientific journals about the Earth’s magnetosphere written by scientists at other institutions. I also write papers about my own work. I attend weekly seminars given by students and scientists working in our department, as well as the occasional visiting scientist, to learn about their research. I have presented results from my research in these seminars, in order to get feedback on my work. A few times a year, I travel to conferences to give presentations on my work to scientists from around the world and exchange ideas with them. In order to obtain funding for my work, I also write proposals to NASA and the National Science Foundation.

  • A room full of rocket scientists

    We're watching the THEMIS launch today.

    The launch takes place at Cape Canaveral in Florida, but we will be watching it here at the Space Sciences Lab over closed circuit tv. There's a lot of excitement in the building today. THEMIS is comprised of five small satellites.

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