A promised follow-up may be found over on Chicago Boyz.
Meanwhile, previously unknown reader (the best kind) Chris Luebcke directs my attention to this news release, which clearly indicates that Cassini-Huygens will be able to signal the success of SOI before returning images of closest approach, and notes: "I only point this out because based on your post I almost--almost!--gave my long-suffering space-o-phobic wife a reprieve from my planned NASA TV marathon tonight. No more!"
Just don't come crying to me if your stuff's piled at the curb tomorrow. ;)
JPL graphic here; nail-biting events are of course the ring-plane crossings, which are to occur tomorrow at 9:11 PM CDT (ascending) and Thursday at 12:56 AM CDT (descending). Throughout SOI, the high-gain antenna will be used as a shield and therefore will not be pointed toward Earth, so the first returned images, and thereby confirmation of success, are not expected until 7 AM CDT on Thursday.
Guessing that the rings are 1 km thick, Cassini-Huygens, which is 4 meters wide, will intercept a total volume of nearly 50,000 m3 on each of its two passes through the gap between the F and G rings, at an angle of about 15° (arrival geometry is depicted on page 38 of this document [400 kB *.pdf]). On the inbound (ascending) crossing, judging by the drawing in the press kit, it will be moving at about 20 km sec-1, and will therefore traverse the ring plane in perhaps one-fifth of a second. The outbound (descending) crossing will be fractionally slower.
What we hope for, then, is that the ~106 m3 of space being swept out by the probe during these events will not contain any substantial ring fragments. At the relative velocities in question, applying KE = ½mv2, we find that colliding with a grain of sand (10 mg) would resemble being shot by an M-16, judging by the figures available here (see ".223 Remington 55 gr SP BT"). Cross your fingers.
-- in which I make a behavioral prediction, is right here.
The ones with me in them, that is. Click here if you dare.
Virginia blogs a looming regulation that looks to make housing in California even less affordable, if that is possible. As an admirer from afar of the Golden State, I am just familiar enough with it to know that its microclimates could seriously affect the feasibility of any such requirement.
To illustrate this -- at much lower resolution, but still effectively: Turning to U.S. Solar Radiation Resource Maps and selecting "Average," "June," and "Flat Plate Tilted South at Latitude," we find insolation varying by about 40% from the vicinity of Humboldt Bay (5.5 kWh m-2 d-1) to that of Death Valley (7.5).
This differential, which is sufficient to suggest that the new regulation is not only economically illiberal but technically nonsensical for northern California, persists from March through October. The other months, it's worse, ranging from 60-120%. In fact, California's intrastate insolation (just try to find that phrase anywhere else!) varies more than that of any other state except Alaska, which I think we can agree is unlikely to adopt widespread photovoltaic power any time soon.
Behold the perils of one-size-fits-all regulation. If the people behind this just can't stand to let homeowners make their own decisions, they should push it at the county level. Just watch out for climatological complexity.
-- if you're in the Western Hemisphere and the weather is good (and it's dark), and look at the really cool conjunction of the Moon and Jupiter.
Another couple of dozen editorials, op-ed pieces, and letters to the editor turned up in a LexisNexis™ search covering English-speaking media yesterday and today. Some juicy excerpts:
TexasBestGrok's John L nails it.
You tell 'em, CERDIP!
And man, some of it's ugly.
See also the timing of this story (original report here), which -- notwithstanding that SpaceShipOne used N2O as an oxidizer rather than ammonium perchlorate -- is a clear signal of potential regulatory roadblock. Then there is the inimitable Democratic Underground -- though I note that even there, most of the reaction was positive, and some comments were downright perceptive.
Meanwhile, a LexisNexis™ search on "SpaceShipOne AND editorial" from Sunday through today gets eight hits as of midday Central time. One was spurious -- a transcript of CNN's American Morning, which mentioned the flight but was not an editorial. Excerpts from the other seven, all of which were overwhelmingly positive:
As noted here, we'll be getting together a week from tonight in the River Market area. Groupies, stalkers, obsessed fans, and formerly unknown readers (the best kind) may spot me by referring to this picture, taken by Alphecca's Jeff Soyer when I dropped by his demesne on the way to see the Transit of Venus (erudite? I thought I was just shooting the, er, breeze).
After Joe Katzman of Winds of Change kindly linked the post below, I posted a comment promising to follow up on a couple of things I'd thought of since drafting it.
First, it occurred to me that Phoebe itself would not be naked-eye visible from a spacecraft in close orbit around Saturn. Its visual magnitude of +16.5 as seen from Earth, ~9.54 AU (1.43 billion km) away on average, translates to +6.3 from the distance of Saturn itself (12.9 million km) -- and it would be even dimmer if it were not "full," that is, nearly directly opposite the Sun. In fact, from any of the inner satellites, you would almost always need binoculars to see it.
(The new Saturnian irregulars are, of course, much fainter, averaging nearly 0.1 AU from Saturn and magnitude +22 as seen from Earth; they would be perhaps 12th-magnitude objects in Saturn's sky, requiring a 4" or larger telescope to be seen.)
Secondly, a question arises as to how Phoebe will be mapped. There is an existing but very low-res map based on the much more distant Voyager 2 flyby, but now that we have spectacular images like this, it will have to be extensively revised. The question arises because longitude 0° is normally defined as the meridian from which the primary (in this case, Saturn) is directly overhead at all times -- but Phoebe is not tidally locked; it rotates every 9 hours and some minutes. There is no sub-Saturnian point to serve as 0° N/S, 0° E/W. What to do?
Ask Phil Stooke, that's what. He responded with alacrity (edited and with links added):
The answer to your question is that there are no rules except in the case of
the synchronous rotators, as your comment correctly suggests. So for objects like this the origin is arbitrary. That being said, there are some common considerations:
So in the case of Phoebe one small crater, probably near the equator in the region seen in the higher resolution images, will be chosen arbitrarily as a marker for zero longitude. The choice will probably fall to the Cassini imaging team members who do the actual Phoebe shape modelling and mapping (ie Peter Thomas and colleagues at Cornell), and their recommendation will (likely) be approved by the International Astronomical Union's Working Group on Planetary Cartography, which I am part of.
A very public thanks to Phil for explaining the process!
I've been trying to post follow-ups to the items mentioned in this list, but have been a lot better about some than others -- I did finally successfully observe comet NEAT/Q4 back on Sat 15 May, for example, but never blogged an observing report. Now Mike Daley sends a reminder of the Phoebe flyby, which is the first event of what we may hope will be a long, successful tour of the Saturnian system by Cassini. Closest approach was yesterday afternoon, just before 4 PM CDT.
Phoebe (typo on page; that darker-than-coal albedo is 0.05, not "0.5") shines at only magnitude +16.5, so it is not among those moons of Saturn easily visible from Earth with an amateur-grade telescope. (Titan can be glimpsed in binoculars and is obvious in almost any telescope; then Tethys, Rhea, and Dione appear next, being of almost equal brightness; Enceladus is more difficult; and Iapetus, being much brighter on its trailing hemisphere, is visible only when near greatest western elongation. This leads to moments at the eyepiece oddly reminiscent of Dirty Harry. "Now did I see five, or did I see six? To tell you the truth, in all this excitement, I just can't remember. And seeing as how this is a 4 mm Televue Nagler, the most powerful eyepiece in the world, you've just got to ask yourself -- do I feel lucky?") Direct visual observation of Phoebe would require a dark-sky site, a good ephemeris, and something about like this, so start saving those nickels and dimes. ;)
Phoebe is in a retrograde (ie backward) orbit inclined at 30° relative to the plane of Saturn's equator, rings, and other moons -- but only ~5° relative to the rest of the Solar System -- and is not tidally locked, with a rotation period of a little over 9 hours; it rotates over 1,400 times in one orbit around Saturn! The photo here shows Phoebe as a battered ellipsoid, which is to be expected, given its likely origin as a KBO and its surface gravity of perhaps 1/400 of Earth's (calculated from info available here). This pair of images includes more information about the relative orientation of both Phoebe and the spacecraft.
Given its inclined orbit, the view of Saturn, its rings, and other moons from Phoebe would be spectacular, resembling this famous shot from Voyager. The rings would subtend about 40' of arc, one-third larger than the full Moon as seen from Earth, and the planet -- when directly opposite the Sun and therefore analogous to a full Moon -- would shine at around magnitude -8.2, which while only 1/60 or so as bright as a full Moon is 25 times brighter than the brightest Venus gets as seen from Earth. Titan would shine at magnitude 0, making it one of the dozen or so brightest "stars" in the sky, and would range nearly 3° away from Saturn as it traversed its orbit. Rhea, Tethys, and Dione would be closer in and fainter, but still comparable in brightness to, say, the stars in Orion's belt.
This ChiTrib story says that images of closest approach are to be transmitted to Earth today. I'll be out of circulation most of the weekend, so you're on your own, I'm afraid. ;)
It was like one of those Ray Bradbury stories set on (pre-Mariner 2) Venus, where it stops raining for five minutes every hundred years. In this analogy, Venus would be Penobscot County; the hundred years would be the 1 hour and 37 minutes of time from local sunrise to the end of egress; and the five minutes would be the ten-second glimpse I actually got from a parking lot in East Corinth, Maine (45°00' N, 69°02' W) at 7:14 AM EDT, when the clouds thinned just enough for the disk of the Sun to appear.
In cheap 10x50 binoculars (unfiltered; the clouds were plenty thick enough -- I had a solar filter with me just in case), no sunspots were visible. Venus was less than halfway through egress but seemed farther along, thanks to the famous black drop effect. Considering that the planet's diameter is only 1/115 that of the Sun, it appeared surprisingly large. From my vantage point, visualizing the solar disk as a clock face, the egress point was at around 3:30.
If I had to pick any 10-second period of the transit to see, this would have been it. I went from glum to elated in the space of a few heartbeats. Seventeen hundred miles by plane and rental car, three vacation days and several hundred dollars burned, and it was worth every bit of it. To look across forty million kilometers of space and see another world silhouetted against the Sun, even momentarily, is an experience not to be missed. As Patricia Reaney of Reuters explains:
The Venusian transit only occurs four times every 243 years. Two are in December, eight years apart, and then 121.5 years later there are two June transits, also eight years apart. After another 105.5 years the cycle begins again.
UPDATE: Realized that the unusual apparent size of Venus must be due to its distance, which after all is only about a third of the way to the Sun.
FURTHER UPDATE -- Tony Ortega writes:
"My wife and I traveled north a couple of hours from Kansas City to Mercer, Missouri, where my sister has a small farm -- and, more importantly, a terrific eastern horizon from her front lawn. My heart sunk, however, when I got up at 5:30 am to find a grey cloud bank parked in the distance to the east. By the time the sun rose over it, I figured, we might see nothing. But our luck prevailed. The reddened disc poked through with Venus still a few minutes from third contact. However, it was far too dim to penetrate the solar filters on my 10-inch Newtonian telescope and its 80mm finder. So, after a brief reassuring test with binoculars, I took off the filters and viewed the sun directly. My sister Cathi took the opportunity to point her digital camera into the eyepiece, and she snapped this shot. Not bad considering the conditions -- sun on the horizon, heavy clouds, and a handheld camera!
"Unfortunately, we missed third contact when the sun passed through some thicker clouds, but after that it brightened, I put the filters on, and we had a very clear view of the planet egressing. Terrific stuff."
As I told Tony, this makes him the second (known) member of the newly-formed Midwestern Association of Unfiltered Solar Observers. ;)
Well, I won't be liveblogging it, but I've got a decent chance of seeing the last couple of hours of the event (full info here). I am posting this from the library at the main campus of the University of Maine, which is located in Orono, just north of Bangor.
Sunrise in Bangor tomorrow morning is at the perfectly ghastly hour of 4:49 AM EDT, a/k/a 3:49 AM CDT. Well, I knew it was a tough hobby when I started it. ;)
Checking Table 1 in the article linked above, we find that greatest transit is at 4:19 AM EDT, half an hour before local sunrise, and egress runs from 7:06 to 7:26 AM EDT. So -- weather permitting -- I will view nearly half of the entire event.
But nobody grazes in here to read about me, so let's do some math. Without showing my work, I find that Venus will block about 1/15,000 of the Sun's light during the event. Doesn't sound like much, but even amateur astronomers can exploit this effect to find large planets in other solar systems. This project used an instrument with a working aperture of only 99 mm to detect Jovian-class planets. If sensitivity increases as the square of aperture, as I infer, a 1-meter telescope should be adequate to detect a transit of an Earth- (or Venus-) sized planet orbiting a main-sequence star anywhere within several hundred light-years of the Solar System, if the plane of the planet's orbit is properly aligned.
Playing with some more numbers, I find that the view from Venus -- well, from above its atmosphere -- of the night sky during the event would include Earth shining at magnitude -6.9 (around ten times brighter than the brightest Venus ever gets as seen from Earth) and the Moon shining at magnitude -2.4 (about as bright as Jupiter as seen from Earth), about four-tenths of a degree east of Earth in the sky.
I also decided to calculate the magnitude of a truly esoteric effect, "Earthshine." We've all seen it as reflected off the crescent Moon -- but how much light will the backside of Venus be reflecting toward us tomorrow? Not very much, to be sure; about one five-hundred quadrillionth as much light as we'll be receiving from the Sun at the same time. But if you could somehow isolate that light, it would equate to a seventeenth-magnitude object, about the brightness of a main-belt asteroid 10 kilometers in diameter.
I'll try to post an observing report by midday tomorrow. Best of luck to any Arcturus readers attempting to observe the event. And remember, if you don't succeed, there's always next time!
Anybody needing a good laugh is advised to graze on over to June 2004...The Beginning Of The End?, which makes several subcultures look very silly indeed. I am not much of a supporter of W, but in fairness I should say that relatively few of those who are will fall for this.
And while I certainly adhere to this, some of my fellow members of set A can be mightily embarrassing.
Not to overlook the obvious, I will gleefully revisit this topic at the end of the month.
The disaster that is Science City, a lavishly publicly-funded facility rendered nearly worthless by incompetent management, is ably deconstructed by (known Arcturus reader) Tony Ortega of The Pitch. Mild language warning.
Ortega explains, in his inimitable style, how the museum occupying Union Station (the imposing structure in the left foreground of this webcam view) came to include one of the best-designed planetariums in the country -- which has languished without a director, much programming, or any publicity. The ASKC is mentioned, by contrast, as a successful organization. Of course, the ASKC is volunteer-run and funded entirely by members' contributions and gate receipts at Powell Observatory.
Without wishing to be unduly cynical, it seems unlikely that local political leadership will draw the proper lesson from this ordeal. RTWT, if you can stand it.
Venus has assumed control:
Memorandum for all council[s], committees, and member societies of the Astronomical League:
(I dropped Bob Gent's name rather extravagantly in A Modest Proposal for an Asteroid Warning System.)
Reason (Founder, Longevity Meme) once again writes, this time to direct my attention to this piece on anti-aging researcher Aubrey de Grey, who is the subject of an article in FORTUNE magazine.
... and Mike Daley writes to direct my attention to this page about the Transit of Venus, which I will be observing the final third or so of (weather permitting) from somewhere in New England or the Maritime Provinces, after a sort of mini-blog-bash in Vermont with Alphecca's Jeff Soyer and a representative of The Bitch Girls (any New England, mid-Atlantic, or nearby Canadian bloggers who wish to join us should contact Jeff; see the Alphecca sidebar for his e-mail).
Excerpts from Parameters, Summer 2004, in which Ralph Peters writes In Praise of Attrition:
We don’t need discourses. We need plain talk, honest answers, and the will to close with the enemy and kill him. And to keep on killing him until it is unmistakably clear to the entire world who won.
Consider our enemies in the War on Terror. Men who believe, literally, that they are on a mission from God to destroy your civilization and who regard death as a promotion are not impressed by elegant maneuvers. You must find them, no matter how long it takes, then kill them. If they surrender, you must accord them their rights under the laws of war and international conventions. But, as we have learned so painfully from all the mindless, left-wing nonsense spouted about the prisoners at Guantanamo, you are much better off killing them before they have a chance to surrender.
Faced with implacable enemies who would kill every man, woman, and child in our country and call the killing good (the ultimate war of attrition), we must be willing to use that power wisely, but remorselessly.
The whole thing is 3,900 words, which translates to ten or twenty minutes of reading time. But my purpose here is not so much to urge you to RTWT as to compare its tone to this, where I quoted from page 406 of GENERATIONS: "Historically, aging Idealists have been attracted to words like 'exterminate' and 'eradicate,' words of apocalyptic finality ..."
Peters' "wisely, but remorselessly" is becoming the watchword of our generation (yes, Peters is a Boomer). And our generation always gets what it wants. Let's hope it wants to be wise as much as it wants to be remorseless.
Returned to Missouri safely Monday afternoon about 4 PM. Lessons learned, in chronological order:
Next trip on the midlifecricycle is tentatively scheduled for 7/30-8/2, in a northerly direction.