Jimmy Webb Telescope Launched Without A Problem

Alec_t

Joined Sep 17, 2013
14,280
Just curious. Why, if there are 18 mirror segments, do we see 8 radial light streaks? 8 is not a sub-multiple of 18.
 

nsaspook

Joined Aug 27, 2009
13,085
https://www.cbsnews.com/news/nasa-webb-space-telescope-near-perfect-focus/

1647529404495.png1647529624313.png
The "rays" extending from the star were caused by the hexagonal shape of Webb's primary mirror segments and so-called diffraction spikes, the result of light bending around the three struts holding the telescope's secondary mirror in place.

Such artifacts are normal with large telescopes and bright, relatively nearby stars. But they do not form around the dimmer stars and galaxies Webb was designed to study.
 
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Alec_t

Joined Sep 17, 2013
14,280
Thanks for the info. But in view of the hexagonal symmetry and three struts I would have expected perhaps 6 'rays' rather than 8.
 

nsaspook

Joined Aug 27, 2009
13,085
Thanks for the info. But in view of the hexagonal symmetry and three struts I would have expected perhaps 6 'rays' rather than 8.
There are 6 major rays and two minor so it's a bit of both.
"Three pairs of diffraction spikes from the mirror borders and smaller horizontal diffraction spikes from the support of the secondary mirror (the other spikes from that are merged with the mirror segment spikes)."
High res photo.
51942047253_8d3205f079_o.jpg
 
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nsaspook

Joined Aug 27, 2009
13,085
https://www.theverge.com/2022/6/8/23160209/nasa-james-webb-space-telescope-meteor-strike-impact
NASA’s new powerful space telescope gets hit by larger than expected micrometeoroid

https://blogs.nasa.gov/webb/2022/06/08/webb-engineered-to-endure-micrometeoroid-impacts/
Webb: Engineered to Endure Micrometeoroid Impacts

A large micrometeroid the size of a small micrometeroid? A "minimeteoroid"?

https://www.esa.int/ESA_Multimedia/...ieved_from_the_Hubble_Space_Telescope_in_2002
ESA built-solar cells retrieved from the Hubble Space Telescope in 2002
1654878463400.png
 
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MrSalts

Joined Apr 2, 2020
2,767
https://www.theverge.com/2022/6/8/23160209/nasa-james-webb-space-telescope-meteor-strike-impact
NASA’s new powerful space telescope gets hit by larger than expected micrometeoroid

https://blogs.nasa.gov/webb/2022/06/08/webb-engineered-to-endure-micrometeoroid-impacts/
Webb: Engineered to Endure Micrometeoroid Impacts

A large micrometeroid the size of a small micrometeroid? A "minimeteoroid"?

https://www.esa.int/ESA_Multimedia/...ieved_from_the_Hubble_Space_Telescope_in_2002
ESA built-solar cells retrieved from the Hubble Space Telescope in 2002
View attachment 269165
If Webb was hit within a few months, it is completely insane that Voyager has been surviving without noticeable problems since about 1975. Is orbiting at a constant distance from earth and sun more likely to cause an impact than traveling away from the center of the solar system? Who knows, so far, the number off datapoints is too low to know. Maybe that was the one in a billion hits and it will be safe for the next thousand or more years. Or, Webb might be disabled by Labor Day from dozens of impacts. .
 

Thread Starter

MrAl

Joined Jun 17, 2014
11,389
If Webb was hit within a few months, it is completely insane that Voyager has been surviving without noticeable problems since about 1975. Is orbiting at a constant distance from earth and sun more likely to cause an impact than traveling away from the center of the solar system? Who knows, so far, the number off datapoints is too low to know. Maybe that was the one in a billion hits and it will be safe for the next thousand or more years. Or, Webb might be disabled by Labor Day from dozens of impacts. .
The Webb is at a Lagrange point. That makes it more prone to collisions i believe.
I talked about this with a friend back before it was launched and this is one thing we both feared. IF it gets hit too much, bye bye space birdie.
 

Papabravo

Joined Feb 24, 2006
21,159
The Webb is at a Lagrange point. That makes it more prone to collisions i believe.
I talked about this with a friend back before it was launched and this is one thing we both feared. IF it gets hit too much, bye bye space birdie.
Isn't it in a halo orbit around the Lagrange point?
 

MrSalts

Joined Apr 2, 2020
2,767
The Webb is at a Lagrange point. That makes it more prone to collisions i believe.
Fun to speculate but, as I said, one datapoint doesn't make a trend unless you have some evidence. Your theory is like saying, "you have a better chance winning the lottery if you pick the same numbers every week vs picking new random numbers each week". I'd like to see the data with an explanation if you have it.
 

Thread Starter

MrAl

Joined Jun 17, 2014
11,389
Fun to speculate but, as I said, one datapoint doesn't make a trend unless you have some evidence. Your theory is like saying, "you have a better chance winning the lottery if you pick the same numbers every week vs picking new random numbers each week". I'd like to see the data with an explanation if you have it.
The point is that there will be more random objects in that vicinity than elsewhere. So speaking in terms of probability, the probability of there being more random objects in the vicinity (or passing through) is higher than any random point. So in other words if it was at some random point it would probably be hit less than where it is now.
 

cmartinez

Joined Jan 17, 2007
8,220
https://www.theverge.com/2022/6/8/23160209/nasa-james-webb-space-telescope-meteor-strike-impact
NASA’s new powerful space telescope gets hit by larger than expected micrometeoroid

https://blogs.nasa.gov/webb/2022/06/08/webb-engineered-to-endure-micrometeoroid-impacts/
Webb: Engineered to Endure Micrometeoroid Impacts

A large micrometeroid the size of a small micrometeroid? A "minimeteoroid"?

https://www.esa.int/ESA_Multimedia/...ieved_from_the_Hubble_Space_Telescope_in_2002
ESA built-solar cells retrieved from the Hubble Space Telescope in 2002
View attachment 269165
Ouch ... I hate that ... it's like buying a brand new Ferrari and then have a pebble crack its windshield right after you drove it out of the dealership ...
 

nsaspook

Joined Aug 27, 2009
13,085
The point is that there will be more random objects in that vicinity than elsewhere. So speaking in terms of probability, the probability of there being more random objects in the vicinity (or passing through) is higher than any random point. So in other words if it was at some random point it would probably be hit less than where it is now.
https://www.researchgate.net/figure...he-L4-and-L5-Lagrangian-points_fig1_254660988
It's something we've seen before at stable points but our L2 is not naturally stable so it's not possible to make predictions about Webb hits from current data IMO.
 

MrSalts

Joined Apr 2, 2020
2,767
The point is that there will be more random objects in that vicinity than elsewhere. So speaking in terms of probability, the probability of there being more random objects in the vicinity (or passing through) is higher than any random point. So in other words if it was at some random point it would probably be hit less than where it is now.
Everything in your paragraph is speculation. You are so positive - saying "will be" and "is higher", based on a single data point that I laughed out loud. NASA's risk analysis hasn't expressed any of what you've said. But please, don't let me stop you from creating facts and trends from a single datapoint. Note that this is the first spacecraft to be positioned in L2.
 
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