Notices by AkaSci 🛰️ (akasci@fosstodon.org), page 19

Total eclipses occur more often in the northern hemisphere than the southern one because -
- Eclipses are more likely in summer, because the Sun is up longer then.
- Summer in the northern hemisphere happens when the Earth is near aphelion, its farthest distance from the Sun for the year, the Sun is a bit smaller in the sky, which favors the occurrence of total solar eclipses and disfavors annular ones.
- The opposite holds for the southern hemisphere.

https://svs.gsfc.nasa.gov/5222
8/n

Here is a look at the positions of the Sun and the Moon today, tomorrow and Tuesday, around 3:00 p.m. EDT.

https://www.timeanddate.com/worldclock/sunearth.html?iso=20240407T1504&n=105
12/n

The NASA APEP mission name takes inspiration from the serpent deity Apep from ancient Egyptian mythology, aka "the Lord of Chaos". Apep is the enemy of the Sun deity Ra and is said to have pursued him and, every so often, nearly consumed him, resulting in an eclipse.

Image below: Ra, in the form of a cat, smiting Apep with a knife. Papyrus of Hunefer, 19th dynasty.

https://sites.erau.edu/sail/APEP/
https://en.wikipedia.org/wiki/Apep
11/n

Here is the famous painting by space artist Pat Rawlings made in 1989, showing the total solar eclipse of 2017 as seen by humans on the moon.

Well, humans have not set foot on the moon yet since the Apollo missions, but hopefully soon ...

https://twitter.com/Patnspace/status/897632376758685698
http://www.patrawlings.com/default.cfm
13/n

You can follow the progress of the NASA WB-57 aircraft at https://www.flightaware.com/live/flight/N926NA and https://www.flightaware.com/live/flight/NASA927
Tail numbers N926NA and N927NA

N926NA took off from Houston (Ellington Field) at 09:57 CDT, heading SW and is currently just off the Mexican west coast at 50,000 feet altitude. It will soon turn around and track the eclipse.
Similarly for N927NA, which took off from El Paso, TX.

15/n

It is E-Day!
Here is the weather forecast and forecast for cloud cover in the path of the total eclipse and the rest of the country.

Please see the rest of this thread for interesting bits of info about this eclipse and eclipses in general.

Happy viewing 😎

14/n

Dallas, a few minutes ago, had this view of the total solar eclipse.
NASA webcast at https://www.youtube.com/watch?v=2MJY_ptQW1o
18/n

Next, another artistic pic by NASA photographer Bill Ingalls, with the Washington Monument's tip piercing the the partial eclipsed Sun, as seen from Washington D.C.

Details and more photos at https://www.flickr.com/photos/nasahqphoto/albums/72177720315879304/
Credit: NASA/Bill Ingalls
20/n

Here are a few outstanding pics of the solar eclipse today from NASA.

First, this composite image of multiple exposures over the Washington Monument, by the esteemed NASA photographer Bill Ingalls.

Details and more photos at https://www.flickr.com/photos/nasahqphoto/albums/72177720315879304/
Credit: NASA/Bill Ingalls
19/n

XKCD comic pointing out that that the difference between 91% (or even a 99%) eclipse and a total eclipse is extremely dramatic. An almost total eclipse is barely noticeable, while a total eclipse is a visual phenomenon unlike any other.

https://xkcd.com/2914/
https://www.explainxkcd.com/wiki/index.php/Main_Page
1/n

This is a prediction of how dramatic the total solar eclipse of April 8 will look like if you are lucky or prepared enough to be in the path of totality.
😲
This image is from a website run by Predictive Science Inc, that uses a "Data-Assimilative, Continuously Running Prediction Model" to create these images, which takes the changing magnetic field around the Sun into account in real-time.

https://www.predsci.com/corona/apr2024eclipse/home.php
2/n

Status update on the Voyager 1 spacecraft which has been sending a 0101 pattern since Nov 2023.

The problem seems to be a failed memory part in the FDS computer; engineers are planning to move ~200 words of software from one region to another, according to Joseph Westlake, director of NASA’s heliophysics division, who was speaking at a March 20 meeting of the National Academies’ Committee on Solar and Space Physics.

Westlake sounded very optimistic.
👍
https://www.nationalacademies.org/documents/embed/link/LF2255DA3DD1C41C0A42D3BEF0989ACAECE3053A6A9B/file/D727AF88E8C806D7A1F75C8401AF9CF23BCCC2EC9F3A?noSaveAs=1
17/n

Some tech. info on the Voyager FDS computer –
- There was a backup FDS unit but it failed in 1981.
- Custom CMOS CPU - 36 instructions. 80 KIPS, 115 kbps data rate.
- 128 registers, kept in memory.
- CMOS memory, a first in space, 8KB.
- No separate memory for program storage vs execution. The CMOS memory is non-volatile kept powered on by the RTG.
- DMA access to memory by hardware. Instead of “cycle-stealing”, the instructions indicated cycles where DMA can occur.

https://ntrs.nasa.gov/api/citations/19880069935/downloads/19880069935_Optimized.pdf
16/n

Looks like the "memory upload" to the Flight Data Subsystem (FDS) on Voyager 1 is taking place at this time from the NASA DSN site in Canberra.
Go Voyager!

https://eyes.nasa.gov/dsn/dsn.html
https://en.wikipedia.org/wiki/Canberra_Deep_Space_Communication_Complex
19/n

It looks like the Voyager team is preparing for a new "memory upload" to the FDS computer on Friday, as evident from the DSN schedule and instructions shown below for Voyager 1.

I am guessing that this is to rearrange the software so that it no longer uses the locations in the faulty memory chip in the FDS. If true, then hopefully we will hear Voyager 1's true voice on Sunday, 45 hours later. OTOH, this may be just one of many steps on the road to recovery.
🤞
https://voyager.jpl.nasa.gov/pdf/sfos2024pdf/24_03_28-24_04_15.sfos.pdf
18/n

It's been 6 hours since the "memory upload" data was transmitted to Voyager 1 from the NASA DSN site in Canberra.

During that time, the signal has traveled about a quarter of the way to Voyager 1, about the average distance to Pluto. The response will arrive at earth on Sunday around 1500 UTC (RTT = 45 hours).

Let's imagine a spacecraft sent to the nearest star Proxima Centauri, 4.2 light-years away. How would we diagnose problems and upload new software to it?

https://eyes.nasa.gov/apps/solar-system/#/home
20/n

All eyes and ears on Voyager 1 as data is being downloaded from it in response to the "memory upload" commands and data sent 45 hours ago.

The DSN Goldstone 70m antenna is receiving data now at 40 bits/s.

Hopefully, the problem with its transmission being stuck at 0101 has been fixed. We will find out this week ...
🤞

https://eyes.nasa.gov/dsn/dsn.html
21/n

Great news on Voyager 1.
Richard Stephenson of DSN Canberra reports that engineering data was being received from Voyager 1 last night at 40 bps.

No science data yet, perhaps because they did not switch to the higher 160 bps rate, but this is a major step towards recovery and validates the diagnosis (failed memory chip in the FDS computer) and fix (rearrange software to bypass the failed memory area).

Now waiting for a status update from NASA.
23/n

NASA Voyager twitter site confirming that Friday's memory upload was intended as a fix for the Voyager 1 transmission problem caused by the failed memory chip in the FDS computer.

"Sister @NASAVoyager's reply to Friday's upload should b arriving now @ Goldstone's 70m antenna DSS-14, hopefully confirming that the Flight Data Subsystem memory update was successful. If so, telemetry should now give clearly interpretable signals with science & engineering data!"

22/n

@noodlejetski
Oops! Corrected. Thanks!