This and most other posts have been moved to: Goingwalkbout.blog
Sneaking Up on Pluto (Part 1)
This and most other posts have been moved to: Goingwalkbout.blog
Sneaking Up on Pluto (Part 1)
Sneaking Up on Pluto (Part 2)
Steve Campbell December 2015 Homepage
I always tend think of the exploration of the Solar System as something everybody knows about and that is probably erroneous for two reasons. First, not everyone was fascinated by the subject at the time, as I was and second, lots of you individuals are not old enough to have been paying attention when it happened. I would assume that some of this is taught in school, but I really can’t say, since it was just beginning to happen when I was at S.P Waltrip High in Houston. Both Shelly Duval and Patrick Swayze had graduated before I got there, in case some fans of either want to know.
One thing that might puzzle the average student might be why we had images of all the Outer planets by the 1970s and 80s and nothing but a dot or smudge for Pluto. That all relates to what was called at the time “The Grand Tour”. As it happened, there was an alignment of the outer planets in the 70’s and 80’s such that it would be possible to use gravity assisted orbital adjustments (“the slingshot effect”) to make it possible for a space probe to visit Jupiter, Saturn, Uranus and Neptune in one long and carefully managed trajectory. That’s another interesting story and I would be happy to tell it later.
Unfortunately, Pluto was not properly aligned to be next in the series of these visits. Why not? One way it was explained to me was: Any trajectory plotted for a probe approaching Neptune to send the probe to Pluto would intersect Neptune itself. So, that is why Pluto remained an unvisited backwater of the Solar System until now.
The alignment of the outer worlds by 2006 was scattered enough that only Jupiter could help send the craft to Pluto and then only in a certain window of time. Missing that window would lengthen then the mission severely or delay the launch by about twelve years until Jupiter came by again. Fortunately, the launch came off well on the first try.
A considerable amount of data was collected in the Jupiter flyby (2). A lot of what was last seen by the Magellan Orbiter was updated and enhanced. Figure AA is a view of the Jovian moon Io which is far more volcanically active than the Earth. That is pronounced with a short “I” by all the Ivory Tower PhD’s and a long “I” by normal people. Major changes in its Geology (Don’t give me a hard time about that word!) were detected.
Many other moons and Jupiter itself were imaged and studied, but we are talking about Pluto, here.
Figure AA: A view of Jupiter’s moon Io as seen from New Horizons during its fly-by of Jupiter Credits: NASA/JHUAPL/SwRI
New Horizons Spacecraft
Figure A is the New Horizons Spacecraft. The main body of the spacecraft is about the size of a grand piano and the whole thing masses as much as a medium sized truck
Figure A: The New Horizons Spacecraft Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
New Horizons (NH) incorporates all that has been learned over the years. The Voyager probes (one of which actually made the complete “Grand Tour”) each had a main antenna that was capable of constant communications with the Earth. This necessitated what is called a “scan platform” that held the instruments that need precise pointing, that moved independently of the antenna. That configuration had proven troublesome on one of the Voyager probes and data were lost. That is because data storage was actually on a ½ inch, 8 track magnetic tape with a total capacity of about ½ Megabyte and a top baud rate of 56 kilobits per second (3). That’s what I said – “stone knives and bear skins!” – so, real-time transmission was required for image data.
The newer probes including NH have fixed instruments that are pointed by turning the entire spacecraft. This in turn means that the probe cannot talk to the Earth and take instrument readings at the same time. What makes it all possible is an enormous memory capacity that is capable of high data rates. This was a luxury that earlier probes could not enjoy. The disagreeable result was that the probe was “radio silent” as it collected the bulk of the science data at Pluto. This is simply because it was busy pointing instrument and taking readings.
That large dish antenna labeled “REX” in the Figure was a lot smaller than they might like but it was also a trade-off to allow more instrumentation. That means that, while the data could be acquired in a big rush during the fly-by, the data return rate was dismally slow by comparison. So much so that the NH is still downloading data, months after the fly-by and will be doing so until November of 2016.
The other instruments are described here as quoted from the New Horizons web site (1):
“The New Horizons team selected instruments that not only would directly measure NASA’s items of interest, but also provide backup to other instruments on the spacecraft should one fail during the mission. The science payload includes seven instruments:
Ralph: Visible and infrared imager/spectrometer; provides color, composition and thermal maps.
Alice: Ultraviolet imaging spectrometer; analyzes composition and structure of Pluto’s atmosphere and looks for atmospheres around Charon and Kuiper Belt Objects (KBOs).
REX: (Radio Science EXperiment) Measures atmospheric composition and temperature; passive radiometer.
LORRI: (Long Range Reconnaissance Imager) telescopic camera; obtains encounter data at long distances, maps Pluto’s farside and provides high resolution geologic data. SWAP: (Solar Wind Around Pluto) Solar wind and plasma spectrometer; measures atmospheric “escape rate” and observes Pluto’s interaction with solar wind.
PEPSSI: (Pluto Energetic Particle Spectrometer Science Investigation) Energetic particle spectrometer; measures the composition and density of plasma (ions) escaping from Pluto’s atmosphere.
SDC: (Student Dust Counter) Built and operated by students; measures the space dust peppering New Horizons during its voyage across the solar system.”
The alert reader will note that the same antenna (REX) that returns data to the Earth is also listed as an instrument. It is used to measure the changes in an Earth-NH transmission as the signal is eclipsed by Pluto’s atmosphere and surface and the same situation was also measured at Charon, thus characterizing the atmosphere of Pluto and of Charon (if any).
A Better View – Like “Way!”
If you are wondering why I have gone on so long about the discovery, naming and early characterization of Pluto, Astute Readers, I will now confess: I wanted to convey – just a bit – that long-delayed anticipation that I felt – literally for years – in awaiting the results of the NH mission. Hence, the title of this article “Sneaking up on Pluto”. That said, I hasten to present a Portrait of the Happy Couple, Pluto and Charon. Please see figure B.
Figure B. Pluto and Charon Credits: NASA/JHUAPL/SwRI
First, I must point out that this graphic is a composite. That is to say that while they are absolutely valid images of Pluto and Charon, they have been cut and pasted into this “Family Album”.
You will no doubt notice some very intriguing and unexpected features of both the planet and its satellite. Far from a near-featureless cratered ice-ball, it is obvious (by lack of craters in some regions) that Pluto has undergone recent changes. There are distinct regions of very different character and color. Charon has a great chasm that spans its diameter and crosses its equator.
The early much interpreted, computer generated images from the scant data received by the Hubble Telescope that indicated differentiated terrain are richly confirmed. The most pronounced feature is the large plain of ice that quickly became known as the “Heart” at this resolution much of it seems featureless and hence craterless. The standard procedure for dating terrain on solar system objects is to count the number of craters of different sizes. When the craters are many and varied, the terrain is obviously very old. When you see an area with no craters, then it is very new, relatively speaking. The Heart was later “officially” named “Tombaugh Regio” in appropriate honor of Pluto’s discoverer.
I should mention that I referred to Tombaugh as a High School Graduate previously, but I feel obliged to point out that he later earned a PhD. My reference to his educational status at the time of the discovery was no slight, but rather was my tribute to the idea that Excellence does not require certification. I have known and worked with many brilliant PhD’s. I have also known and worked with some who were so over-specialized as to be (in my humble opinion) rather shallow and uninteresting people, outside of their rather small zone of competence.
The smooth-looking part (on the left) of Tombaugh Regio is now called “Sputnik Planum”. As we will see in the next images, it is not nearly as featureless as it first appeared.
Pluto in Detail
I will take a leap forward now to some of the most up-to-date images. Figure D is a close-up of the dark region near the Southwest of the Tombaugh Regio. It covers a confluence of three terrain types, the smooth, icy plains at top, the mountains (obviously not associates with craters) in the center and more “conventional” cratered landscape at the bottom.
Figure D: The Dark Area at the Southwest of Tombaugh Regio. Please note the three distinct terrains Credits: NASA/JHUAPL/SwRI
The icy plains are now revealed to have distinct polygonal divisions. The ice in question is actually solid Nitrogen and Methane which, at the ambient temperature of about -230° C behave much like Earth-temperature water ice and flow slowly into valleys as they accumulate. The Mountains at the center of this image are quite clearly not related to craters and probably contain a large fraction of water ice which at Pluto temperatures is as hard and durable as rock. I will cite the good Doctor Shenck (4), again for this insight.
Pluto has been moving farther from the Sun since 1985 and you might expect that the atmosphere could be condensing out to be frozen on the surface. What did puzzle me was the contention that we have no evidence of Pluto’s atmosphere actually freezing out as it moves farther from the Sun. I asked Doctor Shenck if there might be some deposition of atmospheric gasses in the seasonal total-dark areas of the Southern hemisphere and if there might be some data (yet to be downloaded) from instruments that might answer that. He replied positively to both questions.
This image in Figure D seemed to me to give some merit to the idea that some atmospheric “fall out” may have already taken place. The crater at lower left in the image, quite clearly indicates that the ice there accumulated, did not flow from anywhere else, but must have condensed (been deposited) out of the atmosphere. Also, I mentioned that the ice appears to be flowing into valleys and I ask you, how can ice flow if there is not a new supply being deposited on the existing mass of ice? For the record, this image was not available when I spoke to Dr. Schenck.
Just during the writing of this article the answers came from this quote from a NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute Press Release:
“Key to understanding activity on Pluto is the role of the deep layer of solid nitrogen and other volatile ices that fill the left side of Pluto’s ‘heart’ — a vast, 620-mile (1,000-kilometre) -wide basin, informally named Sputnik Planum. New numerical models of thermal convection within this ice layer not only explain the numerous polygonal ice features seen on Sputnik Planum’s surface, but indicate this layer may be up to a few miles thick. Evaporation of this nitrogen and condensation on higher surrounding terrain leads to glacial flow back toward the basin; additional numerical models of nitrogen ice flow show how Pluto’s landscape has been and is still being transformed.”
Figure E is a higher resolution image from the edge of the Tombaugh Regio that shows much more texture to the icy plains and a much better look at the mountains.
Figure E: High resolution color image at the edge of Tombaugh Regio Credits: NASA/JHUAPL/SwRI
Figure F is an even higher resolution of another region of the icy plains. Notice how the ridges that divide the segments are seemingly being covered up with what look like dunes to me. I don’t know what to think of those. But the aforementioned press release indicates that there is a Nitrogen/Methane cycle of evaporation and condensation that drives the glacier-like accumulations. It seems that these gasses play the role of water on Earth, that exists in solid, liquid and gaseous forms on the same planet. Now, there is no evidence (yet) of any liquids on Pluto and I suspect that the cycle is one of sublimation (solid to gaseous) and deposition (gas to solid).
Figure F: Higher resolution image of the icy plains Credits: NASA/JHUAPL/SwRI
Despite the previously mentioned low data rate, the data are accruing at an overwhelming rate and the unmitigated diversity and complexity of this information will no doubt keep Planetary Scientists employed for years to come. I really need to publish this before it gets even further obsolete. But one thing is clear. Pluto is far from the static, frozen, cratered, icy rock it was imagined to be. It is a dynamic and complex world and IMHO, deserves the designation of “Planet” without qualifiers.
Still, it is a tantalizing irritation that the New Horizons probe only provided a “snap shot” of the situation at Pluto and we can only find out what happens next by a similar, massive effort to launch another such probe. It is perhaps a comfort to remember that the technology of the New Horizons probe is about 15 years out-of-date now and the next such probe would be faster, better, cheaper and -especially- less massive. It is not unreasonable to imagine that a Pluto orbiter could be within the realm of possibility. Even if decades later, a new probe could see the changes and the longer the delay, the more obvious those might be.
Steve Campbell November 2015
Sunspots have been studied for over 400 years by such notable Scientists as Galileo. Many earlier observers had noticed that the sun was occasionally marked with darker spots. But, Galileo spread the word about sunspots and many of his contemporaries subsequently took up regular observations of same.
Observation of Sunspots
Right here is where I will repeat a warning that you may have heard a hundred times before: Do not look directly at the Sun and especially DO NOT look at the Sun in a telescope. The only exception to that last part is where a Qualified Astronomer is using a proper solar filter or is projecting an image from a telescope onto a screen.
That Galileo made use of a telescope around this time was strictly coincidental. Observations of the Sun were done during sunrise and again at sunset when it is possible to notice large sunspots with the naked eye, without damaging that eye. The sunlight passes obliquely through the atmosphere and is very much attenuated.
An image of the sun can be projected by a “camera obscura” which is essentially a darkened room with a tiny opening – literally, a “pin hole”- through which the sunlight enters. For reasons we won’t go into here, a pin hole acts like a lens and focuses light. By careful placement of a screen of cloth or paper, a focused image appears, large and bright enough to sketch. The astronomer Johannes Kepler was known to have used this system to view the sun. In an interesting side note, Kepler thought he was seeing the planet Mercury passing between the Earth and the Sun, instead of a spot on the sun itself. Had he checked on the following day, he would have seen the same spot and because he knew that a Mercury transit would not last a day, he would have seen his error.
The method of projecting an image from a telescope onto a screen was developed by a protégé of Galileo named Benedetto Castelli.
“It was Castelli who developed the method of projecting the Sun’s image through the telescope, a technique that made it possible to study the Sun in detail even when it was high in the sky”. (1)
The following quote explains a bit about the “Sunspot Number” which was established as the metric of sunspot activity.
“Continuous daily observations were started at the Zurich Observatory in 1849 and earlier observations have been used to extend the records back to 1610. The sunspot number is calculated by first counting the number of sunspot groups and then the number of individual sunspots.” (2)
I would be remiss if I did not include actual images of sunspots with this discussion. Figure A shows a recent image of the sun taken by the Solar and Heliospheric Observatory (SOHO). This is a NASA space probe that orbits between the Sun and the Earth constantly monitoring the Earth-facing side of the Sun.
Figure A: SOHO image for November 22, 2015 22:30 UT
By the method described (Count the groups and multiply by ten then add the number of individual spots), I would estimate the sunspot number to be between 35 and 45. Don’t quote me. I know there are limits to how small individual spots can be and still be counted, but I don’t know what those rules are.
Figure B shows an image of the Sun during the Cycle 23 Maximum.
Figure B: Cycle 23 Maximum – May not be SOHO
I am not sure of the origin of this image, it may not be from the SOHO probe, but in any case, it illustrates the difference between high and low sunspot counts. Again, I don’t do this for a living, but I would guess the count here to be well over 100.
Figure C shows the accumulated sunspot numbers over the last 400 years of solar observations.
Figure C: 400 Years of Sunspot Observation
It is ironic that Galileo took an interest in sunspots and popularized such observations just in time for the Maunder Minimum when sunspots gradually became rare phenomena. The Maunder Minimum is associated with the Little Ice Age, when weather was cooler than today. The numbers of that time are plotted in red because they are yearly averages due to the sparsity of observations. The blue are monthly averages, results of sustained, systematic observation. The Maunder Minimum is still a valid conclusion, but the data cannot be said to be “high resolution”. The later Dalton Minimum is much better defined and typically associated historically with “Dickensian Winters”. In recent years, those types of winters are returning to England.
Figure D is a plot of NASA Sunspot Numbers for the two previous and the current sunspot cycles. It clearly shows the declining trend.
Figure D: Nasa Sunspot Numbers, Cycles 22, 23, & 24
Magnetism and the Climate Connection
It is the changing magnetic field of the Sun that drives the existence or absence of sunspots. The Solar magnetic field changes on a long time scale and with different periods of oscillation. The most obvious of these is an eleven-year cycle that will is obvious in Figure C. The magnetic properties actually reverse in polarity in each new cycle, which makes it a twenty-two-year cycle in reality. Periods of high sunspot activity are associated with high magnetic field strength and a dearth of sunspots is an indication of low magnetic intensity.
A plot of terrestrial magnetic field strength in Figure E demonstrates the cyclical nature of the terrestrial magnetic field as influenced by the sunspot cycle. (3)
Figure E: Terrestrial Magnetic Index
As indicated by the note in the seventies, periods of lower terrestrial magnetic field strength are associated with colder weather. This effect has been explained by the work of Henrik Svensmark (6) who demonstrated that magnetism effectively blocks cosmic rays. But, when the field strength is low, the increase of cosmic rays makes cloud formation increase and global temperatures drop. Now that the Ap index has dropped to unprecedented lows and the global temperatures have failed to increase as predicted by many, this association would seem to be confirmed.
The fact that ”official” temperatures have not actually dropped may have something to do with the manipulation of those datasets by certain individuals who have reduced the number of weather stations averaged from over 6000 to about 1500 and shifted the average latitude of those stations from that of Oklahoma City to that of Hawaii (5). Please note that before they began eliminating stations, the average was indeed, dropping! See figure F.
Figure F: Global Historical Climatology Network (GHCN) temperatures and station count
Steve Campbell February/March, 2016
You may never have thought about surgery on your eyes, and with any luck you may never have to experience this problem. Or, you may be facing this problem and wonder about what to expect. It sounds very serious and, with any imagination at all you can come up with some really scary possibilities.
Well, you can stop worrying after you read about my surgery.
I vaguely remember – from my very early years – my Great Uncle Ben, who wore what we called “coke bottle bottom” glasses and was legally blind. He came in to our house one time (yes, somebody drove him there) and he tried to hang his hat on the corner of the mirror on the wall. I reckon he made out a vague figure of some old man trying to hang a hat there and when in Rome…
I don’t know what Ben’s ailment was, but I doubt it was cataracts, since surgery has been possible for that, actually for centuries. I mention him because I, too was losing my vision – and at a younger age (60) than Ben. In my case, it was cataracts. I looked up this definition:
“Normally, the lens in the eyes are clear or transparent. However, a cataract is an abnormal clouding or opacity of the eye’s crystalline lens. The opacity can lead to a decrease in vision and possibly blindness.
Cataracts are thought to develop as a result of age-related degenerative alterations to the proteins in the lens. Smoking, diabetes and steroid use may also be contributing factors to the development of cataracts.” (1)
It started when I noticed that my eyeglass prescription was quickly becoming inadequate. In fact, I could now see better without my glasses. However, the stars at night were now all “doubles” and all oriented the same way. That orientation changed when I tilted my head. A natural reaction to double vision – closing one eye – did nothing to change this. This is called an astigmatism and I thought that was the only problem. I even tried the Driver’s eye test, and to my surprise, my left eye could not read, nor even tell that the numbers existed. With the right eye and with both eyes I could clearly read. At no point did I notice any “clouding”.
I made a visit to the eye doctor and he found that my vision had changed dramatically, especially on the left. He also diagnosed cataracts developing in both eyes. My father had cataracts when he was my age so, I was not surprised. Worried yes, but not surprised. While I had been a smoker, I quit in 1994, when my father was permanently on oxygen with chronic obstructive pulmonary syndrome, due directly to 50+ years of smoking. Oddly, I still smoke in my dreams, but that is another story. So, I don’t know if smoking did it, or just age, but the eye-doc referred me to a surgeon, who evaluated the left eye and scheduled surgery.
There are several ways to do this and it will be your decision how your vision changes.
First, you can opt, as I did, to have a fixed-focus lens implanted. This will give you 20/20 vision at a distance, but you will still need reading glasses.
You can have one lens set for distance and one for reading. That will let you read without glasses, but require glasses for driving.
You can have a “multi-focal” lenses implanted, eliminating any need for corrective lenses, altogether.
I did not choose the multi-focal option. I asked how the eye “selected” which focus to use. As I understand it, the brain picks which focus to use. Think of a screen on a window. You can focus on the view out the window or the screen itself. I am afraid it was not very convincing. I can only afford to do this once. I did know some people with fixed-focus lenses and they seemed quite happy with them. The multi-focus option also costs more.
As for the near/far combination option, I figured that if I need glasses for driving, they would be prescription. And, I would need a spare pair and sunglasses. However, if I need glasses for reading, I can buy them at most dollar stores or get a six-pack at Sam’s for cheap.
As I pointed out to the pre-op crew, everything you do in this place would make your mom yell at you! Do I put on pajamas? No, they just cover my street clothes with a hospital gown. Take off my shoes to go to bed? No, they just cover those with a couple of shower caps. The eye is rendered numb by some eye -drops that (rather inappropriately) sting like the Dickens! After that they roll me off to keep my eye open while they poke it with sharp things. Mom wouldn’t like that, either.
The surgery sounds scary at first. They will break up my natural lens and suck it out with a small tube. The artificial lens will then be inserted through the same incision where it will expand and anchor itself in the “pouch” where the natural lens had been. When you add in the fact that I will be conscious and that eye will be open – I don’t know about you – but that scared the “willies” out of me!
You may doubt me, but it is not as bad as it sounds. The anesthesiologist served up an I.V. dose of something that made me think, “Shoot, this ain’t so scary!”. They stain the natural lens with some dye, so all I “saw” was some shifting colors. Once the implant lens is in place, the improvement is startlingly, impressively obvious.
The colors are suddenly brighter and more vivid. The implant even allows a bit of the ultraviolet light that a natural lens would block. During World War two the British used cataract patients to pass secret messages in light that was invisible to everyone else. I did some research on this and could only find a Car Talk puzzler that mentions this phenomenon. (2) I can tell you, though, that I heard this from an Astronomy professor back in the 70’s. Also, it is mentioned somewhere in Isaac Azimov’s vast body of work and an Astronomer named Walter Scott Houston used his new “super-vision” to observe stars that “normal” people could not see. (3)
Comparing the “good” eye to the “bad” one was something I could not stop doing. The “clouding” of the still-cataract affected eye was now “blindingly” obvious. The walls in the recovery room were a light brown through the right eye or pure white through left. The Moon is dirty brown (right) or bright silvery color (left). The gas flame on the stove is a pale, grayish blue (right) or a deep, rich blue (left).
You will need someone to drive you home. The eye will feel “scratchy” and inflamed for a few days and you may notice the edge of the lens in your peripheral vision. Bright lights cause some headaches and I wore dark glasses (kindly provided in my hospital “swag bag”) for weeks afterward.
They told me that once I had the worst eye fixed, I would notice how bad the other really was. I did and it got worse, so we did the right eye about two months later. It is a different and very distinctly visible world, now. I really did not know what I was missing. This is one thing that has really made me quite happy in the last few months, which have tried my soul otherwise.
Steve Campbell March 2016
Neptune was the first planet to be discovered by mathematical means. After the discovery of Uranus and subsequent observations of the Seventh Planet, it was observed that its orbit was not meeting expectations of Kepler’s Laws. It was determined that there must be another planet -farther away – that was influencing the orbit. That planet was later discovered and quickly thereafter found to have a large satellite. (1)
Neptune is the farthest Giant Planet from the Sun and not surprisingly the last to be visited by a spacecraft. In the old days, when your author was young, they called Jupiter, Saturn, Uranus and Neptune “Gas Giants”. Now they reserve that title only for Jupiter and Saturn and call Uranus and Neptune “Ice Giants”. As you may know the now call Pluto and Eris “Dwarf” Planets (I can’t agree with that). As of today, Mercury, Venus, Earth and Mars are still “Terrestrial Planets”. But soon, it seems to me, each planetary body will have its own unique category.
Quoting from my two-part series “Sneaking Up on Pluto”:
“One thing that might puzzle the average student might be why we had images of all the Outer planets by the 1970s and 80s and nothing but a dot or smudge for Pluto. That all relates to what was called at the time “The Grand Tour”. As it happened, there was an alignment of the outer planets in the 70’s and 80’s such that it would be possible to use gravity assisted orbital adjustments (“the slingshot effect”) to make it possible for a space probe to visit Jupiter, Saturn, Uranus and Neptune in one long and carefully managed trajectory.”
Any path that could have slung Voyager 2 from Neptune to Pluto would have crashed the probe into Neptune itself. Knowing that, the mission planers arranged to take a good close look at Neptune’s large moon, Triton (not to be confused with Saturn’s big moon, Titan). It was thought at the time that Triton might be a lot like Pluto because Triton is in a highly inclined and retrograde orbit around Neptune. That indicates that Triton may well be a “captured” moon that was similar to Pluto. Triton is actually a bit larger than Pluto (1680 km vs. 1464 miles in diameter). Now that we have seen Pluto, it turns out that the two are quite similar.
The Voyager II Spacecraft
Again from Sneaking Up on Pluto (Please see link below):
“The Voyager probes (one of which actually made the complete “Grand Tour”) each had a main antenna that was capable of constant communications with the Earth. This necessitated what is called a “scan platform” that held the instruments that need precise pointing, that moved independently of the antenna. That configuration had proven troublesome on one of the Voyager probes at Saturn and data were lost. That is because data storage was actually on a ½ inch, 8 track magnetic tape with a total capacity of about ½ Megabyte and a top baud rate of 56 kilobits per second (2). That’s what I said – “Stone Knives and Bear Skins!” – so, real-time transmission was required for image data.” Voyager was – despite my demeaning reference – quite advanced at the time and some of its imagery is still quite impressive.
The image below depicts the identical Voyager 1 and Voyager 2 Spacecraft. (4) The dish antenna is 3.7 meters in diameter (12 feet, 2 inches) across. The arm extending to the right contains the main experiments and the imaging “scan platform”. The left arm holds the three radioisotope thermoelectric generators that power the probe. The gold disk on the “body” is the famous CD with messages and images of Earth for anyone “out there”. This CD was a pet project of Carl Sagan. Carl has been inserted into the picture at the proper size to give it a sense of scale.
This photo is from his brief and little-known “Fonzarelli” period. Raise your thumbs, Carl!
Figure A: The Voyager Spacecraft NASA/NASA website
About time we got around to the planet, I hear you thinking. I have a table of planetary statistics (3) that serves as a good introduction for any planet. You may expect to see this table in future posts. Please see Figure B, below.
Figure B: Table of Planetary Statistics NASA
You will notice that Neptune has 17 times the mass of the Earth and about 3.9 times the diameter. That only works out that way because the mean density of Neptune is 30% that of Earth. If it were as dense as the Earth, Neptune (of the same diameter) would have 60 times the Earth’s mass. All four Giant Planets are low-density like that, but Neptune is the densest of them. Likewise, all Giant Planets are fast spinning and Neptune is slower than most, rotating in 16 hours. The Navy has adopted a 16 hour rotation of duties and sleep aboard out nuclear subs, so submariners would be right at home on Neptune. Just a small tangent, I’ll get back on track, now.
Figure C: Neptune as seen by Voyager 2 NASA/JPL
The clouds were somewhat of a surprise after the Voyager’s views of Uranus – which was almost featureless. The big dark spot (named rather predictably, the “Great Dark Spot”) was another surprise as were the winds (1500 mph) stirring these features around. These are the fastest winds in the all the Planets (5) and unexpected out in the cold dark zones of the outer Solar System.
Neptune takes 164 years to orbit the Sun. It’s a long wait for Summer, eh? Neptune, like all Giant Planets (plus Mercury and Earth) does have a magnetic field and in fact, it is much stronger than the Earth’s. That would seem to indicate that it has an iron inner core. But it cannot be very large, or the overall density would be larger. It is in fact estimated that the core part of Neptune at its center is about Earth-sized. Most of what is above is water, ammonia and methane (CH4) ice (estimates vary for thickness). That is considered to be its “mantle”.
The atmosphere above that is hydrogen, helium and methane. The white clouds you see vary in composition depending on pressure. The higher clouds where pressures are about Earth-like (1 bar) are probably methane vapor. Lower down and at higher pressures are clouds of ammonia, hydrogen sulfate and even water vapor, like the clouds on Earth.
How thick each of these layers might be is still open to interpretation and you can find many differing diagrams, most with no dimensions mentioned. So, having looked at those, I will guess that the core is 4000 miles in Radius (about the same radius as Earth), the icy mantle extends another 10,000 miles above that and the gaseous atmosphere another 1400.
Later photos of Neptune by the Hubble Space Telescope have shown considerable changes in Neptune’s atmosphere, since Voyager.
Triton is the largest moon of Neptune and by no coincidence, the first discovered (17 days after the discovery of Neptune, itself). It is unique in several respects. It is the only “large” satellite to orbit in a “retrograde” sense. By large, I mean to say that it is near to the size of our own Moon. By retrograde, I mean that it orbits in a direction opposite to the rotation of its planet. That and the high inclination of Triton’s orbit seem to indicate that it was captured. For reasons we won’t go into, it is easier for a moon to be captured in a retrograde orbit than otherwise. Jupiter and Saturn have lots of former asteroids as moons, but they tend to be small and far away. Triton is so close that it is being slowly pulled closer to Neptune and in several billion years will be shattered into a ring like Saturn’s. You might expect a captured moon to be in an eccentric orbit that varies in distance from its planet, but Triton’s orbit is so close to exactly circular that the difference is not worth mentioning. It stays at about 220,483 miles from Neptune which, coincidentally is about the same distance from the Earth to our own moon. It orbits Neptune in 5.8 days and rotates in the same time. That is to say, it keeps the same side toward Neptune, just as our Moon does to Earth. Now, some of my readers are sharp enough to notice that our moon takes 28 days to orbit. Why so different if the distances are near the same? The difference, of course is that Neptune is 17 times as massive as the Earth, as I mentioned a few paragraphs ago. This will be on the test! 😉 Figure D, below is a Voyager 2 image of Triton
Figure D: Triton NASA/JPL
All other large satellites orbit the same way and are therefore by definition, prograde. Triton also looks quite distinctively different from most other planetary satellites, which tend to be rather uniform and crater covered (admittedly with many exceptions). It has an atmosphere that, while very thin, has detectable clouds. It shares the much modified and differentiated characteristics that we now know of on Pluto. That tends to confirm the “capture” hypothesis.
You may ask, “Just how does a passing object become “captured”? “. There are several ways. One would be for Triton to have collided with a smaller moon, as it passed near Neptune. That might slow it just enough to wind up in an orbit. As it would have collided with a prograde moon, that would be especially effective since that would almost double the velocity difference between the two and quadruple the energy delivered to the passing Triton. That should have left a mighty crater on Triton. While nonesuch was seen by Voyager, such a crater could have since been covered by the glacier-like deposits of Nitrogen ice (the part that looks like cantaloupe peel) that are visible in Figure D. Likewise, that crater might have been in the darkened part of Triton, that was not visible when the Voyager went zooming by at the greatest velocity ever given to a man-made object (at the time)
A second possibility would be “gas drag” as Triton passed through the upper atmosphere. That would seem unlikely, unless Neptune had a more extensive atmosphere at the time. Since it may have been captured billions of years ago, that is entirely possible, but still just speculation.
Another possibility was detailed in a paper by Craig Agnor (University of California, Santa Cruz) and Douglas Hamilton (university of Maryland) in 2006. (6) First, I should explain that Pluto and all the other Smaller Planets out past Neptune have been designated as Kuiper Belt Objects (KBOs). If Triton had been one of a co-orbiting binary pair of KBOs, it is possible that a pass near Neptune would have captured it, while at the same time, ejecting its companion to a more distant orbit of the Sun. It all has to do with relative motion of the three bodies. This hypothesis has the virtue of not relying on chance collisions or hypothesized “greater atmospheres”. This idea was made more believable by the discovery that many KBOs are indeed, binary. Not the least of these is Pluto, who’s biggest satellite (Charon) is about one half its own size. It has been estimated that 15% of KBOs may be binary in nature. That a KBO could have come near to Neptune is not unlikely since Pluto itself comes nearer the Sun than Neptune as it was during the late years, last Century. Having said that, I must also remark that Pluto is now in a resonance with Neptune that keeps the two safely apart. I mean to say, that when Pluto comes nearer to the Sun, it is still very far from Neptune and always will be.
But, all in all, I think these guys are very near the mark with their hypothesis.
Neptune is another fascinating member of the Solar System and I learned a lot by researching to write this article. I hope you find it interesting as well. You may wonder why I do this. Well, those of you who know me know that I suddenly have time on my hands. It is a blessing…and a curse. ;-). Also, I have always had a fascination with the Solar System that goes back to my days in Elementary School.
You and I are truly fortunate to live in a time when these mysterious dots of light in the sky that were the Planets are now becoming known as Great Worlds, many that dwarf the Earth in size and complexity and others that are revealing the secrets of Nature that have been heretofore unknowable.
Steve Campbell January 17, 2016
SpaceX has put another payload into orbit following December’s successful return to flight. Their fortunes have improved since last year’s failure of a Space Station Resupply mission.
Quoting Space Exploration Technologies (SpaceX) Press Release:
With this mission, SpaceX’s Falcon 9 rocket will deliver the Jason-3 satellite to low-Earth orbit for the U.S. National Oceanic and Atmospheric Administration (NOAA), National Aeronautics and Space Administration (NASA), French space agency Centre National d’Etudes Spatiales (CNES) and the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT).”
“Jason-3 is the newest satellite in a series designed to maintain long-term satellite altimetry observations of global sea surface height. These data provide critical ocean information that forecasters need to predict devastating hurricanes and severe weather before they arrive onshore.”
Launch took place in California. Again from SpaceX press kit:
“Space Launch Complex 4E at Vandenberg Air Force Base, California SpaceX’s Space Launch Complex 4E at Vandenberg Air Force Base has a long history dating back to the early 1960s. Originally an Atlas launch pad activated in 1962, 4E was in active use until a 2005 Titan IV launch. SpaceX’s groundbreaking was in July 2011, and the pad was completed in November 2012 in just 17 months.”
The Vandenberg facility is built to accommodate the Falcon Heavy vehicle as well as this version of Falcon9. The California site is necessary for the orbital requirement of a 66 degree inclination. Launching such a mission from Florida would require passage over populated areas instead of the Vandenberg trajectory over the Pacific Ocean.
The launch went nominally and the satellite was successfully deployed. The “hosted video” is available ate this link:
The action starts at 19 minutes and 23 seconds. I will warn that a substantial fog was in place for the launch. Also, I should admit now that the attempted landing by the first stage on a barge at sea was almost successful as well. The “almost” means that one landing leg collapsed during a faster-than-anticipated approach. There is no video yet available on this but I expect it will be another of those “blown-to-bits” events.
But this was, of course, a secondary goal. The SpaceX team landed a first stage the last time on land at Landing Complex 1 at Cape Canaveral Air Force Station last December. There is a Landing Complex being prepared at Vandenberg, but for this mission and rocket, the fuel to return to land is just not available.
The “Success” part comes from the correct insertion of the satellite into the proper orbit. And that, of course, is the “bread and butter” that makes these attempted returns (i.e., “Icing on the Cake”)possible.
SpaceX Brings One Back
Steve Campbell December 2015
Space Exploration Technologies (SpaceX) has returned to spaceflight after a long hiatus with a spectacular success. The private space launch company successfully deployed eleven communication satellites in a text book space launch for ORBCOMM that was as near to flawless as makes no difference.
In a secondary, but historic mission goal, they brought back an orbital-class first stage rocket to its departure point and landed it intact. Figure A is a photo of the returned first stage at its landing zone in Florida. The full video (see Reference #1 – below) should not be missed.
Figure A: Falcon Nine First Stage Landing
Decades in Imagination, Years in the Making
The “fly-back booster” is not a new idea. Engineers have long thought that the “beer-can” approach (use once and throw away) was not an optimal solution, to say the least. Their aim was to eventually adopt a “beer stein” approach that reused the hardware and only required fuel and maintenance between flights. As for how long ago this idea was considered, the “beer” analogy should give you a clue. That particular terminology came from Werner von Braun and his team of German Rocket Engineers. That is to say about 1945-1960.
The Space Shuttle accomplished this, at least in part by reusing the orbiter with its three main engines that were a part of the first stage and the solid rocket boosters that parachuted into the ocean, to be retrieved and reused.
The SpaceX accomplishment is distinct in that an entire, operating and now flight tested rocket has been retrieved. This is superior to the solid rocket booster scheme in many ways. Most notably, the Falcon 9 has not been soaked in seawater. It could in theory be launched again within a week. But, practically speaking, they will certainly want to examine this first returned stage with a fine-toothed comb to see just how much maintenance and repair might be needed.
While Musk’s company is paid by the federal government for launches of satellites and cargo to the Space Station, the reusable aspect of the launch vehicle is being developed privately and independently by SpaceX. The first actual tests of such hardware began in 2012, with a prototype landing-capable rocket stage called “Grasshopper”. It was retired after many successful tests and a successor called (F9R Dev) made just a few flights before it had to be aborted for range safety reasons (i.e., blown to bits) due to a failure in 2014.
There were two attempts to land a first stage of an actual commercial launch – again, a secondary goal to the mission of launching the satellites. The landing zone in both these cases was a station-keeping barge out in the Atlantic Ocean. Both saw the rocket descending over the barge, but both ended in failure (that “blown to bits” thing again). Before those episodes, there were several first stages brought back to simulate landings. Simulate – because the barges were not quite ready and so the stages ended up in the ocean anyway. This last and very successful landing was at an vacant Florida Air Force Air Station launch pad (not far from the launch pad) that has been reconstructed into “Landing Zone One”.
The story of this success would not be complete without some mention of the DC-XA. This was a NASA project that was distinct for its affordable and capable aspects. The project culminated in a sub-orbital rocket to demonstrate vertical takeoffs and landings. Figure B: is a screen capture from the youtube video found at the link in reference number 2, below. The video reveals not only the impressive maneuverability of the craft, but also details the ultimate fate of the one-of-a-kind vehicle.
Figure B: The DCXA Prototype – Screen Capture from Video (2)