Space Eyes See Back In Time

Stunning astronomical and astrochemical images and discoveries reinforce the importance of electronic micro devices and technologies in deep space studies.
  • The amazing images and scientific knowledge that comes from advances in astronomy, astrochemistry and (someday) astrobiology wouldn’t be possible without ever-increasing advances in electronic micro-devices and technology. This appreciation was re-enforced by Zaheer Ali, Senior Manager for the USRA Science and Mission Operations, in his DesignCon 2020 keynote address about NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) and other camera, spectroscopy and related measurements. His visually stunning presentation started with the earliest single pixel detectors that first measured the intensity of stars, to the microchips that first imaged the pillars of the universe, and also looked at the newest cutting-edge devices that are going to be launched soon. What follows are portions of his talk.

  • First Telescope

    The human eye was our first space image detector. It has 576 megapixels or approximately 0.3 meters at one-kilometer resolution. On a beautifully clear night at the Aoraki Mackenzie International Dark Sky Reserve in New Zealand with the Milky Way displayed above us, we can see about 5,000 stars at best.

  • Largest Digital Space Camera

    Now compare the human eye to the most advance camera in the (unclassified) world. The Rubin Observatory, currently under construction on Cerro Pachón in Chile, is an 8-meter-class telescope coupled to a 3.6 gigapixel camera – the world's largest digital camera ever fabricated for optical astronomy. The Rubin Observatory, formerly known as the Large Synoptic Survey Telescope (LSST), will produce the deepest, widest, image of the universe. Each image in the telescope will be the size of 40 full moons. It will be able to “see” 37 billion stars and galaxies. In terms of data, the telescope will generate 1,000 pairs of exposures and 15 Terabytes of data every night!

    The large synoptic survey telescope (see image) destined for the Rubin Observatory is actually a collection of detector arrays that will reveal over 7 million objects in our own solar system. That's not even counting all the objects that we keep mining out of the Hubble Telescope deep field, explained Zaheer Ail.

  • HIRMES

    It all started here at Bell Labs with the first 8 bit charge coupled device (CCD), (see left-hand-side image). We’ve progressed a long ways since then (see right-hand-side image). These are the two detectors for what is going to be the High Resolution Mid-InfrarEd Spectrometer (HIRMES), the newest instrument that is being built for the Stratospheric Observatory for Infrared Astronomy (Sofia) telescope.

    Light will be splayed across these different detector plane arrays. What’s displayed here is an engineering device meaning it is not what's going to be delivered finally to Sofia. It is merely a test device that is based on a technology called transition edge sensing. This approach works down at very low superconducting temperatures where the resistance is near zero. But it's actually an area of transition that is of measurement interest because it has a linear slope to it. Scientists and engineers love linear slopes in measurement systems.

  • Photons at mil-Kelvin

    This image is a closeup of one of the pixels of the detectors (left part of image), which is part of a large planary area of a Silicon-Nitride (Si3N4) isolation system. As a photon comes in (right side of image), it'll hit some sort of absorbing material such as tin (Sn). There might be an attachment medium or the photon might just be deposited directly. This is then connected to a thermistor, a small device that will vary its resistance with temperature. Notice that these arrays are on the Silicon-Nitride window and not the other architectures. The reason is that these devices are at 200 mil-Kelvin. In other words, fractions of a degree above absolute zero! And any power input at all will be spoofed as signal. That is why this system is as isolated as much as possible.

  • How Does It Work?

    How does this whole thing actually work? First, an energy source emits radiation which is absorbed. Remember that thermistors are a glorified thermometer. The thermistor has a thermal link to some sort of refrigeration scheme. Now, this is where the earlier discussion on the superconducting transition area comes into play. There is a linear region between the superconducting and normal parts of the resistance vs. temperature curve (see image). After many calculations, you can determine the photons energy amount. That information can be used as a spectrometer or to count photons, which is used by telescope. Wavelength differentiation is achieved by putting filters in front of measuring device.

  • Cameras And Polarimeter

    Understanding this science and other information has allowed engineers to build the High-Resolution Airborne Wideband Camera-plus, or HAWC+, on SOFIA's telescope (see image). The upgraded camera not only makes images, but also measures the polarized light from the emission of dust in our galaxy. With this instrument, scientists will be able to study the early stages of star and planet formation, and, with HAWC+’s polarimeter, map the magnetic fields in the environment around the supermassive black hole at the center of the Milky Way.

  • Glowing Dust From A Black Hole

    The camera and measurement systems have been the focus of the discussion up to this point. Now let’s see a few examples of how these detectors can be used. The image on the right is taken from a Near Infrared Camera and Multi-Object Spectrometer (NICMOS), an instrument used for infrared imaging and spectroscopic observations of astronomical targets. NICMOS detects light with wavelengths between 800 to 2500 nanometres. The image was taken looking towards the center of the galaxy. It’s fortunate that planet Earth sits on an outer spiral arm of the galaxy as it give us a tremendous amount of stars to study.

    What you can see on the right-hand side of the image is the glowing dust that is being ripped apart by a massive black hole close to the center of the galaxy. Notice the min-spiral-like influences? They seem relatively quiescent, which was unexpected near a black hole. It took some time and observations from other sources to confirm that it was indeed glowing space dust from a black hole.

  • Design An Elegant Experiement …

    Here is the same field of view but taken with the HAWC+’s polar metric data, which amazingly reveals field lines of a massive galactic scale. It implies that the magnetic field lines are controlling the inflows into the black hole. This was something very unexpected. It would explain the quiescent, the relatively calm nature of the mass flows at the center of the galaxy.

    This wholly unexpected result was only possible because engineers and scientist continue to drive improvements in the instrumentation and the micro devices. This is how great science happens. Ali shared the advice from one of his professors: “If you design an elegant experiment, the physics will reveal itself to you.” The same holds true for the devices, i.e., if one can design an elegant instrument, the physics will also reveal itself.

  • Astrochemisty Finds HeH+

    Let’s switch from cameras to a spectrometer. By doing so, one sacrifices spectacular spatial resolution and collapses it into a single pixel. In other words, dynamic range is sacrificed as well as spacial resolution to get extreme spectral resolution. This shift, this sacrifice, enables a molecule hunting expedition! This is astrochemistry. Someday we hope to make it astrobiology but that day is not yet here. Molecule hunting shows up as squiggly lines in the spectra. Quantum mechanics tells us that every state of matter has an energy footprint.

    In the planetary nebula NGC 7027, SOFIA detected helium hydride (HeH+), a combination of helium (red) and hydrogen (blue), which was the first type of molecule to ever form in the early

    Universe. This is the first time helium hydride has been found in the modern universe. This molecule should be present in some parts of the modern Universe, but it has never been detected in space — until now. This was only made possible by the right instruments making measurements at the right position, enabled by SOFIA.

  • What Lies Ahead?

    There are a couple of missions farther out such as the origin space telescope (OST), so called because it’s mission is to look back in time as far as infrared will allow to perceive the origins of the universe (see left-hand side image). This is the first space mission to directly incorporate polar metric imaging thanks to the current success of the HAWC+ system. The design and integration of every past generation of technologies influences the next generation of devices.

    Further, the Parker Solar probe is going to look at fields around the sun (see right-hand side image). This system is reaching the sun. The data from this probe is already being reduced and a major paper on the results should be forthcoming very soon. The detector looks like a black light (see image) due to the intense UV illumination of one of the detectors.

  • Device Advancement Essential for Next Generation

    In ending, consider a recent image formed by the Spitzer and Sofia data. This is a very special image as it was the last one for the Spitzer, which was shuttered in late January. The Spitzer did for infrared what Hubble did for optical images. It allowed a look at the universe using infrared, which was a capability that wasn’t really available before. The ending of the Spitzer and the start of the Sofia are important. Such progressions of science allow us to see things we haven’t seen before. Here, the Sophia is filling in regions that the Spitzer couldn’t because it was saturated. This progression is happening in other fields of science, where we take the results from previous generations of experimental systems and fill in a lot more information with newer or different systems. This is a capability enabled by device advancements in terms of performance, power, size and the like.

 

John Blyler is a Design News senior editor, covering the electronics and advanced manufacturing spaces. With a BS in Engineering Physics and an MS in Electrical Engineering, he has years of hardware-software-network systems experience as an editor and engineer within the advanced manufacturing, IoT and semiconductor industries. John has co-authored books related to system engineering and electronics for IEEE, Wiley, and Elsevier.

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