APOD: Perihelion to Aphelion (2020 Jan 09)

Comments and questions about the APOD on the main view screen.
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Ann
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Re: APOD: Perihelion to Aphelion (2020 Jan 09)

Post by Ann » Tue Jan 14, 2020 5:46 pm

neufer wrote:
Tue Jan 14, 2020 4:25 pm
TheZuke! wrote:
Tue Jan 14, 2020 4:00 pm

How are things in Tralfamadore?
(Not, how were things in Tralfamadore, or how will things be in Tralfamadore.)
So it GOES
Neufer designed IR filters for NOAA's GOES Sounder???

Seious???? :shock: :shock: :shock:

Ann
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neufer
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Re: APOD: Perihelion to Aphelion (2020 Jan 09)

Post by neufer » Tue Jan 14, 2020 7:55 pm

Ann wrote:
Tue Jan 14, 2020 5:46 pm
neufer wrote:
Tue Jan 14, 2020 4:25 pm
TheZuke! wrote:
Tue Jan 14, 2020 4:00 pm

How are things in Tralfamadore?
(Not, how were things in Tralfamadore, or how will things be in Tralfamadore.)
So it GOES
Neufer designed IR filters for NOAA's GOES Sounder???

Seious???? :shock: :shock: :shock:
As "Seious" as I ever get.

It was the last generation of NOAA's GOES Sounder... with just one left over the Pacific:

http://cimss.ssec.wisc.edu/goes/rt/view ... ct=gsc_b12

So it GOES
Art Neuendorffer

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Re: APOD: Perihelion to Aphelion (2020 Jan 09)

Post by TheZuke! » Tue Jan 14, 2020 8:29 pm

neufer,
Was it GOES-5 that had "its lights burn out"?

I recall meteorologists (early 1990's) referring to a GOES satellite lost its IR capability because a carousel of Infrared lamps (needed to calibrate the camera?) used up all of its lamps.

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neufer
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Re: APOD: Perihelion to Aphelion (2020 Jan 09)

Post by neufer » Tue Jan 14, 2020 8:42 pm

TheZuke! wrote:
Tue Jan 14, 2020 8:29 pm

Was it GOES-5 that had "its lights burn out"?

I recall meteorologists (early 1990's) referring to a GOES satellite lost its IR capability because a carousel of Infrared lamps (needed to calibrate the camera?) used up all of its lamps.
  • They only let me work on the secondary instrument: the atmospheric sounder.
https://en.wikipedia.org/wiki/GOES_5 wrote:
<<The primary instrument carried aboard GOES-5,
the Visible Infrared Spin-Scan Radiometer or VISSR, failed in 1984.>>
https://en.wikipedia.org/wiki/Doublethink wrote:
<<Doublethink is the act of simultaneously accepting two mutually contradictory beliefs as correct, often in distinct social contexts. Doublethink is related to, but differs from, hypocrisy and neutrality. Also related is cognitive dissonance, in which contradictory beliefs cause conflict in one's mind. Doublethink is notable due to a lack of cognitive dissonance—thus the person is completely unaware of any conflict or contradiction.

George Orwell invented the word doublethink (as part of Newspeak) in his dystopian novel Nineteen Eighty-Four. In the novel, its origins within the citizenry is unclear; while it could be partly a product of Big Brother's formal brainwashing programs, the novel explicitly shows people learning doublethink and Newspeak due to peer pressure and a desire to "fit in", or gain status within the Party—to be seen as a loyal Party Member. In the novel, for someone to even recognize—let alone mention—any contradiction within the context of the Party line is akin to blasphemy, and could subject that person to disciplinary action and the instant social disapproval of fellow Party Members.>>
Art Neuendorffer

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Ann
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Re: APOD: Perihelion to Aphelion (2020 Jan 09)

Post by Ann » Wed Jan 15, 2020 4:41 am

neufer wrote:
Tue Jan 14, 2020 7:55 pm
Ann wrote:
Tue Jan 14, 2020 5:46 pm
Neufer designed IR filters for NOAA's GOES Sounder???

Seious???? :shock:
As "Seious" as I ever get.

It was the last generation of NOAA's GOES Sounder... with just one left over the Pacific:

http://cimss.ssec.wisc.edu/goes/rt/view ... ct=gsc_b12

So it GOES
Sorry about the spelling mistake. I make them more these days. :(

But hey, Art, tell us a little more! When exactly did you work on GOES Sounder? What year or years? How did you land the job? What exactly was your task designing this thing - making mathematical calculations, running simulations?

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Re: APOD: Perihelion to Aphelion (2020 Jan 09)

Post by alter-ego » Sun Jan 26, 2020 10:51 pm

[float=][/float]
Chris Peterson wrote:
Sat Jan 11, 2020 12:05 am
MarkBour wrote:
Fri Jan 10, 2020 11:48 pm
...
It may be that Jupiter is the most influential planet for this, but I note that in the text accompanying the table (see the last link in the APOD caption) one finds the statement:
Due of the gravitational perturbation of the Moon (and to a much lesser extent the planets), Earth's actual distance at perihelion can vary from 0.9831914 AU (147,083,346 km) to 0.9833860 AU (147,112,452 km).
That leads me to believe that the timing of the lunar orbit versus Earth's orbit is the most influential factor causing the variations.
Yes, that could be right. It makes some sense if you look at the slightly scalloped shape of Earth's orbit because of the Moon. It would be interesting to look at the path of the Earth-Moon barycenter rather than just the path of the Earth.
...
I wondered the same thing.
I used JPL Horizons to answer that and other questions. I analyzed distances from the Sun to Earth, Sun to Earth-Moon Barycenter, and took the difference of two data sets to get the Earth to EMB distances (projected onto the Sun-Earth radial axis). I also analyzed all component distances with respect to the Solar System Barycenter (SSB). These latter analyses were enlightening but, because of posting space and time, is not discussed here. The timeline for all calculations is 200 years (1900 to 2100) with 1-yr time intervals (200 pts), and I used perihelion times that are within 8 minutes of AstroPixels' times. The AstroPixels data is also plotted for reference.

Conclusions:
  • The AstroPixels Perihelion blurb is confusing and wrong:
    1. AstroPixels average (mean) Perihelion estimate leads to confusion.
      As shown in plots, perihelion distances increase at a linear rate of 17.6 km/day (~6,400 km/century). IMO, AstroPixels' average perihelion calculation confuses the interpretation of the variation about the "mean" perihelion as well as suggesting some fundamental importance to the 2.28x multiplier of the Earth's equatorial diameter. AstroPixels chose to define the "mean" as the midpoint perihelion value (essentially the perihelion at year 2000) and, as they stated, the 2.28x multiplier applies to the 29,200-km peak-to-valley (p-v) perihelion range over 200 years from 1900 to 2100. However, from my experience, it's unusual to define a peak-to-valley (p-v) variation about a "mean" when there is a non-random (linear) component buried in the p-v values (i.e when a varying "mean" is not accounted for). Given the linear upward trend of perihelion distance, it's clear the multiplier value will depend on how long the total analysis time interval is. When the perihelion data is corrected by removing the slope of the longer-term systematic drift, the perihelion p-v range is reduced 30% from AstroPixels' data. Therefore, the more useful (and more constant) multiplier is now 1.58x.
      The take-away is that, as presented, there is nothing special about this parameter, it's only an empirical result for the specific circumstances considered.
       
    2. The contribution from the other planets is significant (>50%). After removing the slopes, component fraction estimates are straight forward over the full 200-year analysis interval. Considering the full 200-yr range:
      • The p-v Perihelion range about the corrected mean ≈20,100 km, NOT 29,200 km
      • With the Moon's orbital component removed, the corrected p-v range in Sun to Earth-Moon Barycenter (EMB) distance
        ≈11,500 km , and
      • The p-v range variation of the Earth-Sun distance due to only the Moon's orbital motion ≈9,800km (2 times Earth-EMB distance at lunar apogee)
        The fraction of EMB distance variation due to other Solar System bodies (primarily the Sun and Jupiter) is
        ≈11,500 km ÷ [11,500 km + 9,800 km] = 54%.
    3. From 1900 to 2100, the Earth reaches perihelion about 1 day later roughly every 57 years,
       
    4. The perihelion is increasing by about 6,400 km per century, and the aphelion is decreasing by the same amount
Plots:
  • All vertical axes are kilometers
  • Unless otherwise stated, left and right plots respectively show uncorrected (raw) data and with slopes removed
  • Horizons Sun-Earth distances here agree with AstroPixels' perihelia within 5 kilometers

JPL Horizons &amp; AstroPixels Perihelia.JPG
  • Horizons (200 years) and AstroPixels (100 years) data are shown.
  • Left plot shows AstroPixels' 200-yr 29,204 km p-v variation and the increasing perihelion distance = 0.176 km per day
  • Right plot (slope removed) shows the less confusing p-v variation = 20,132 km
    The more time-independent multiplier = 20,132 km ÷ 12,756 km = 1.58, NOT 2.28

JPL Horizons - Sun to EMB.JPG
  • Shown are the Horizons Sun-to-EMB distances → As mentioned earlier, the contribution from the moon's orbit is subtracted out in these plots.
  • Left plot shows the increase distance rate = 0.177 km/day
  • Right plot shows the p-v variation over 200 years = 11,503 km The distance variation of the EMB component is significant.
    Without doubt, the other solar system bodies are driving the increasing perihelion distance over time, and the contribution to 200-yr p-v variation in perihelion distance is at least 50%

JPL Horizons - Earth to EMB_2 &amp; Perihelion Date.JPG
  • Left plot shows component of Earth's motion, wrt the EMB. Calculated by subtracting the Sun-Earth distance from the Sun-EMB distance at the same time, it is the distance projected onto the Earth-Sun radial axis.
  • The 9,800-km p-v is consistent with 2 times the Earth-to-EMB distance at lunar apogee
  • Because the asynchronous lunar orbital period wrt to Earth's year, the plot is dominated by aliasing. Interestingly, the upper ~74 peaks over 200 years define an average period ~2.7 years which also happens to be the rough period between Blue Moons (using the 7-Blue Moons every 19 years rule-of-thumb).
     
  • Right plot shows the perihelion date increasing about 1 day every 57 years
Well, the answer is a definitive YES to the question about the impact significance of the other solar system bodies on Earth's Perihelion & Aphelion. The analyses using the SSB as the origin generate the same component results but with slightly larger distance errors (±100 km instead of ±5 km). As I said, this exercise was enlightening. By the end, I couldn't help but feel the Earth is on a roller coaster ride bobbling along with a 2.5 million kilometer p-v.
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