Infinite in All Directions: Juno’s Problem, Evolution of Astronomy, Visualising Pulsars

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An artist's impression of a pulsar and its white dwarf companion. Caption and credit: esoastronomy/Flickr, CC BY 2.0

An artist’s impression of a pulsar and its white dwarf companion. Caption and credit: esoastronomy/Flickr, CC BY 2.0

The problem with Juno

The following is an annotated version of a NASA press release published on February 17. It illustrates how a communicator can disguise, rather reconfigure, bad news as good news without in fact lying or hiding anything from the reader. As you can’ll see below: The adverse outcomes of the development are pushed to the press release’s bottom while embellishments are played up to give the impression that nothing major has happened and, in fact, everything’s just as awesome as it was before. The text in blue is mine. The text in bold is added emphasis.

NASA’s Juno mission to Jupiter, which has been in orbit around the gas giant since July 4, 2016, will remain in its current 53-day orbit for the remainder of the mission. This will allow Juno to accomplish its science goals, while avoiding the risk of a previously-planned engine firing that would have reduced the spacecraft’s orbital period to 14 daysThe press release begins with an assurance that Juno’s science goals will be accomplished while it doesn’t yet say what this ‘risk’ is – a curiosity gap intended to keep the reader reading.

“Juno is healthy, its science instruments are fully operational, and the data and images we’ve received are nothing short of amazing,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate in Washington. “The decision to forego the burn is the right thing to do — preserving a valuable asset so that Juno can continue its exciting journey of discovery.” More embellishment while refusing to reveal what the risk mentioned in the lede might be, even as an expert is introduced to defend the decision to avoid it.

Juno has successfully orbited Jupiter four times since arriving at the giant planet, with the most recent orbit completed on Feb. 2. Its next close flyby of Jupiter will be March 27.

The orbital period does not affect the quality of the science collected by Juno on each flyby, since the altitude over Jupiter will be the same at the time of closest approachThis is an interesting line: when Juno was launched and its orbital profile around Jupiter was publicised scientists had been keen to emphasise the importance of a 53-day orbit first and then a 14-day orbit to get “up close and personal” with the planet, when – according to PI Scott Bolton – the primary science phase would begin. In fact, the longer orbit provides new opportunities that allow further exploration of the far reaches of space dominated by Jupiter’s magnetic field Juno’s 53-day orbit does indeed perform some great observations because its flyby distance is really low (~5,000 km) and will hopefully allow it to catch up over time with the objectives of the 14-day orbit thanks to its ‘spinning bangle’ path (image below). However, it isn’t clear if Juno’s no longer being able to orbit Jupiter for more than 10 hours at a time (equal to one day on Jupiter) will imperil some science missions, increasing the value of Juno’s researchAnd if the last six words are true, surely mission scientists would have thought of this earlier? Why didn’t they stick to the 53-day orbit instead of announcing a 14-day orbit down the line?

During each orbit, Juno soars low over Jupiter’s cloud tops — as close as about 2,600 miles (4,100 kilometers). During these flybys, Juno probes beneath the obscuring cloud cover and studies Jupiter’s auroras to learn more about the planet’s origins, structure, atmosphere and magnetosphere.

The original Juno flight plan envisioned the spacecraft looping around Jupiter twice in 53-day orbits, then reducing its orbital period to 14 days for the remainder of the mission. However, two helium check valves that are part of the plumbing for the spacecraft’s main engine did not operate as expected when the propulsion system was pressurized in OctoberAnd there we have it! The real reason the orbital profile has been changed is something has broken onboard Juno. Therefore, the risk mentioned in the first paragraph is in exacerbating this problem – not in jeopardising “the value of Juno’s research”. The difference lies in what motivated the decision: Telemetry from the spacecraft indicated that it took several minutes for the valves to open, while it took only a few seconds during past main engine firings.

“During a thorough review, we looked at multiple scenarios that would place Juno in a shorter-period orbit, but there was concern that another main engine burn could result in a less-than-desirable orbit,” said Rick Nybakken, Juno project manager at NASA’s Jet Propulsion Laboratory in Pasadena, California. The risk is finally fully fleshed out at this point: “The bottom line is a burn represented a risk to completion of Juno’s science objectives.”

Juno’s larger 53-day orbit allows for “bonus science” that wasn’t part of the original mission design. This, of course, is making-do. I’m not saying this is a bad thing; to the contrary, in fact. But do bear in mind that this wasn’t the original mission design, and the saving grace of  “bonus science” has come to be only because the helium check valves have gone awry. Juno will further explore the far reaches of the Jovian magnetosphere — the region of space dominated by Jupiter’s magnetic field — including the far magnetotail, the southern magnetosphere, and the magnetospheric boundary region called the magnetopauseAll awesome objectives, but what about Juno no longer being able to do the science it could have only had it entered the 14-day orbit? In effect, NASA seems to have failed to mention that a glitch onboard Juno has forced it to change its primary mission itself. Understanding magnetospheres and how they interact with the solar wind are key science goals of NASA’s Heliophysics Science Division.

“Another key advantage of the longer orbit is that Juno will spend less time within the strong radiation belts on each orbit,” said Scott Bolton, Juno principal investigator from Southwest Research Institute in San Antonio. “This is significant because radiation has been the main life-limiting factor for Juno.” Again, I have to ask, it seems quite unlikely that mission scientists didn’t think to leave Juno in its 53-day orbit forever. The radiation problem was definitely known at the time Juno was made: Nybakken has referred to it as a “solar-powered armoured tank”.

Four paragraphs after this discuss the scientific results that have resulted thus far from Juno’s observations.


What is astronomy?

Astronomy may be the oldest natural science in the world. Before humans ever took to systematically studying the skies, we were craning our necks upwards, observing the curious movements of some bright points of light, and the stillness of others. Civilizations around the world have incorporated astronomical observations into everything from their architecture to their storytelling…

These are the opening lines in an article that appeared in Astronomy magazine, titled How Islamic scholarship birthed modern astronomy. And the lines triggered a deeper sensation in me than they might have intended: the article, soon after, begins to discuss how the Islamic Empire’s Golden Age, paralleling Europe’s Dark Ages, drew upon Ptolemy’s Almagest to fashion many of the tools and ideas that shaped the evolution of astronomy since, far before Europe could get on it.

More than being a natural science, astronomy to me seems to be the porto-pursuit. Almost all the ancient civilisations – Indian, American, Mesopotamian, Chinese, Greek, Roman and Babylonian – built observatories to look deeper into the sky. Eclipses were logged for their mystifying effects on sunlight; lunar cycles followed for their effects on the ebb and flow of rivers; manuals conceived to use the stars for mariners to find their way on the high seas; and the Sun’s clockwork journeys through the sky used to lodge Earth at the centre of the universe. What we got as a result were our first sense of spirituality, agriculture, trade and a purpose.

It was clear even then that the lights in the sky had a lot to offer: it’s not for nothing that the earliest computer built (150-80 BC) was the enigmatic Antikythera mechanism, to predict the paths of the Sun, moon and the planets. Understanding them was, in many ways, a significant endeavour because all those civilisations understood that the sky was a resource they all shared and bonded over.

Ultimately, it’s hard to imagine that one of the first things that fascinated the first intelligent humans wasn’t the sky above. That it wasn’t the moon’s silver gaze and the multitude of pearly stars floating in a gentle sea of perfect black. That they didn’t look up in unfettered wonder at this celestial dance that played out in infinite patterns. That the moon’s coming and going and the stars’ weaving dance with unceasing regularity didn’t strike them with awe, loneliness, apprehension, fear and ultimately hope.

For a time, it’s hard to imagine that they awakened to witness anything else more unfathomable. Over the many millennia since, more passions have been kindled by astronomy than anything else – if only because looking into the universe helped us situate ourselves as equal humans in others’ eyes, and found our aspirations on the threshold of the universe’s inviting vastness and so understand who we are and where we come from.

And in so tracing this evolution of ideas backwards, the article in Astronomy highlights how we might be giving the Islamic Empire far less credit than it deserves.

Throughout this time, from the beginning of the Golden Age until the early Renaissance, many universities and madrasas, or schools were being constructed around the Islamic empire. In 859 AD the first university was built in Fez, Morocco. It was conceived of and started by Fatima al-Fihri, the daughter of a wealthy merchant. Scholars from all over the world including Christian and Jewish scientists traveled there to study astronomy, math and philosophy.

Many schools and mosques around this time were overseen and managed by Muslim women who themselves had been educated in subjects ranging from literature to algebra, a form of math also perfected by Islam. One of the most well known astronomical tools called an Astrolabe was created by the Greek thinker Hipparcus but was perfected by islamic scientists, particularly women. Mariam al-Astrulabi was a Syrian female astrolab maker from the 10th century. She’s best known for perfecting the art of making these instruments which calculated the altitude of celestial bodies in the sky. In her honor, astronomer Henry E. Holt named a main belt asteroid after her in 1990.

(A final grouse I have about the perception of astronomy itself: this historiography – the progression from the straightforwardness of the early years to the devious sophistication that floods scientific research today – is what makes me sad when the people with the authority to make great things possible are contrarily able to view astronomy as a pursuit indifferent to the human condition. It’s as if we have let our wonderment become victimised by the tragic memories of our own mismanagement.)


Visualising pulsar signals

David Kaplan, an astrophysicist at the University of Wisconsin, Milwaukee, built a device to show what the signals received from a pulsar by a radio-telescope would look like. This isn’t the sort of device that has a screen or an antenna to receive signals, etc. It is in fact an artful visualisation that uses acrylic sheets, a small computer, an LED matrix and some software input to recreate pulsar signals in real-time and in three dimensions. Before I confuse you further – here’s what it looks like:


Kaplan calls it the ‘Pulse-O-Matic‘.

A pulsar is the collapsed core of a dead star. It will have formed when a massive star would’ve run out of light elements to fuse in its core, its outer layers rapidly imploding towards its core. When they impact the core, it becomes compressed to extremely high levels, and its protons and electrons combine to form neutrons. If the core was heavy enough, even the neutrons would’ve become packed in impossibly densely, eventually forming a blackhole. But if the core wasn’t dense enough, then the neutron degeneracy pressure will hold the neutrons apart and bounce the outer layers of the star outward in an explosive flash called a supernova. The core in this state is called a neutron star, an exceptionally dense, rapidly rotating, super-hot, super-magnetised ball of neutrons. Sometimes, the intense magnetic field wrapping around this object focuses a beam of charged particles along the axis of the magnetic field. Because the neutron star is rotating, this beam sweeps across Earth’s telescopes like a pulse. Thus, the object is a pulsar.

Using his Pulse-O-Matic, Kaplan has visualised the pulsating signals received from pulsars by telescopes operated by the US National Radio Astronomy Observatory.


Other bits of interestingness

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