Flying By Mercury

The ESA/JAXA BepiColumbo spacecraft took these pictures of Mercury during its first gravity assist flyby of the planet. During its seven-year cruise to the innermost planet of the Solar System, BepiColombo makes one flyby at Earth, two at Venus and six at Mercury. It will finally arrive in orbit around Mercury in 2025.

Video Credit: ESA / JAXA

Staring at the Sun

On 29 April, 2015, three satellite observatories—NuSTAR, Hinode, and Solar Dynamics Observatory—all stared at our Sun. This image merges data from  Nuclear Spectroscopic Telescope Array, or NuSTAR (high-energy x-rays shown in blue), Japan’s Hinode spacecraft (low-energy x-rays in green), and SDO (extreme UV in yellow and red). The blue-white NuSTAR data pinpoint the most energetic areas.

Image Credit: NASA  /JPL-Caltech / GSFC / JAXA

It Wasn’t a Complete Waste of Time

Video Credit: NASA

I had a small part in the development and construction of the Soft X-ray Spectrometer. In order to be sensitive to energy of individual photons, the detector had to be kept very cold at a very constant temperature. I was responsible for the analog electronics in the system that powered and controlled the last three stages of the refrigeration system. Our team was able to maintain the sensor array at 0.05 K (±0.000001 °K). That’s 5/100 of a degree above absolute zero.

Venus in Infrared

Venus in IR_AkatsukiJAXA, the Japanese space agency, has a satellite orbiting Venus. Akatsuki took this photo of cloud patterns on the nightside of Venus from a distance of about 100,000 kilometers. The camera used sees at a wavelength of 2.26 microns, a wavelength at which the planet’s hot lower atmosphere radiates. This infrared light is blocked by clouds in some places but not others, silhouetting the clouds. Combining this data with data from other wavelengths and more images taken over time, Akatsuki scientists hope to watch the three-dimensional motion of Venus’ atmosphere.

Image Credit: JAXA

Another Flare

quad-flareDuring a December, 2013, solar flare, three satellites watched a current sheet form. This animation shows four views of the flare from the Solar Dynamics Observatory, the Solar and Terrestrial Relations Observatory, and JAXA’s Hinode. The current sheet is a long, thin structure, especially visible in the views on the left. Those two animations depict light emitted by material with higher temperatures, so they better show the extremely hot current sheet.

A current sheet is a very fast, very flat flow of electrically-charged material, extremely thin compared to its length and width. Current sheets form when two oppositely-aligned magnetic fields come in close contact, creating very high magnetic force.

Image Credits: NASA / JAXA

Hitomi (Astro-H)

This video from JAXA describes some of the astronomy that the Hitomi (Astro-H) mission will be doing. It mentions that the the Soft X-ray Spectrometer on board operates at very low temperature. That’s correct. 50 mK. That’s 0.05 degrees above absolute zero. I was a member of the engineering team at Goddard Space Flight Center that designed and built the refrigeration system that maintains the sensor array as that cold operating point with within (±0.000001 °K). I’m looking forward to sharing data from the mission with the Gentle Readers.

Video Credit: JAXA

Up and Away

The weather finally cleared at the Tanega-shima launch facility, and JAXA successfully launched the Astro-H mission. We should begin seeing science data from the mission after a few weeks of shakedown procedures on orbit.

Video Credit: JAXA

The engines are lit just past 20:00 in the video.

A New X-ray Astronomy Satellite

On Friday, the Japan Aerospace Exploration Agency (JAXA) will be launching their sixth satellite dedicated to X-ray astronomy, ASTRO-H, from the Tanegashima Space Center in Kagoshima, Japan. The launch is scheduled at 3:45 a.m. EST.

The observatory carries a state-of-the-art instrument and two telescope mirrors built at Goddard Space Flight Center. That instrument is the Soft X-ray Spectrometer which is able to detect individual low-energy x-ray photons. The SXS detector is cooled to 0.05 degrees above absolute zero, and to keep system noise within useful limits, the operating temperature is held constant ±0.000001 degrees. I was the analog electronics engineer for the team that designed the temperature control system for the SXS.astro-h_illo_labels_0

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Image Credit: JAXA

UPDATE—JAXA has announced that the ASTRO-H launch has been postponed because of high winds at the launch facility. The next possible launch date is on Sunday.

Stay tuned.

Asteroid (25143) Itokawa

25143 IkokawaThis picture of Asteroid 25143 Itokawa comes from the Japanese Hayabusa spacecraft during its close approach in 2005. Itokawa may be a contact binary formed by two or more smaller asteroids that have gravitated toward each other and stuck together. The Hayabusa images show a surprising lack of impact craters and a very rough surface studded with boulders. The asteroid has been described as a “rubble pile.” The asteroid’s density is too low for it to be made from solid rock, meaning that Itokawa is not a monolith but really a “rubble pile” formed from fragments that have been drawn together over time.

Image Credit: JAXA

The Big Chill

During my time at NASA, I worked on subsystems for a couple of instruments used for x-ray astronomy. The first was the Burst Alert Telescope which is a key part of the Swift satellite. The BAT detects gamma ray bursts and provides information to steer the satellite so the other instruments aboard can observe the new x-ray event. My main contribution was the low-noise power regulators that run the detector array. I also design the pulse-width modulation regulator that were a part of the thermal control system for the sensors. They operate at 295 K (±0.5 K), which is roughly room temperature.

The most recent instrument I worked on was the Soft X-ray Spectrometer that is scheduled to fly on the ASTRO-H mission. ASTRO-H is a Japanese mission with NASA providing the SXS instrument. I worked on the temperature control system for the sensors in the SXS.

The SXS not only detects x-ray photons but also measures the energy of individual photons. When a photon hits a surface and is absorbed, the energy transferred to the target warms it. Of course, an individual photon doesn’t have much energy, so for the warming to cause a significant percentage change in the temperature, the target has to be really cold. In the case of the SXS, really cold means 50 mK, that’s 50 millikelvin or 0.05 degrees above absolute zero. To put that level of cold into perspective, its about the same percentage change from room temperature is as room temperature is below the surface temperature of the Sun. And for the changes caused by photons to be noticeable, the variation in sensor temperature allowed by the control system must be less than 1 µK. That’s one microkelvin or 0.000001 K.

OK, liquid helium at low pressures has a temperature of around 1.3 K. That’s the coldest naturally occurring matter in the Universe. How do you get colder than that? The answer involves salt, but not in the same way we use salt in ice cream freezers. My next post on this subject will explain how.