Editing 2564: Sunshield

{{comic
| number    = 2564
| date      = January 5, 2022
| title     = Sunshield
| image     = sunshield.png
| titletext = RIP the surface of Mars
}}

==Explanation==
{{incomplete|Created by THE JWST - Please continue expanding and improving the explanation. Do NOT delete this tag too soon.}}
JWST stands for {{w|James Webb Space Telescope}}, a space telescope launched about 2 weeks prior to publication of the comic. It has a {{w|James Webb Space Telescope sunshield|sunshield}} to protect its instrumentation from the heat of the sun and to keep them below 40 K (-233 °C/-388 °F). The sunshield was deployed the day before the comic was published. The JWST has to undergo a sequence of deployment steps to unfold parts that had to be packed for launch. This sequence has 344 possible points of failure that would render the very expensive space telescope useless, 75% of them were leading up to the successful full deployment of the sunshield. Thus successful steps are widely celebrated. This comic is an example of such a celebration.

Ordinary cameras use a {{w|Flash (photography)|flash}} to take pictures in low-light situations. Outer space is very dark{{Citation needed}}, so this comic posits that the JWST has a very powerful flash to compensate for this. In reality, astronomical cameras don't use flash photography -- they depend on the light either emitted by objects themselves (e.g. stars) or from nearby very bright objects (e.g. planets in the Solar System reflect light from the Sun). A flash wouldn't work because:
* It would take too long for the light of the flash to return to the telescope, at least twice the time again that it had already taken for the original image to arrive on its own, and
* There would not be enough 'flash' light returning, due to it uselessly scattering in all directions. Instead, mirrors and/or lenses focus the light, and long exposure times are used to collect enough of the current light to form a decent image.
* A flash powerful enough to overcome the previous difficulty would have to be inordinately powerful. This which would raise significant questions about powering it, and would damage (or at least startle) many of things the flash would still be able to illuminate.

There is, however, the {{w|Lunar Laser Ranging experiment}} which uses lasers, which are loosely related to flashes for photography, to measure the distance between Earth and Moon. The outward light is concentrated upon the rough area of the lunar target, which employs an {{w|Retroreflector|optical trick}} to send most of that which actually struck it back to the rough area of the ground-based equipment.

The comic assigns the sunshield a new, comical purpose of shielding the sun and earth (which is roughly in the same direction as the sun, due to the deployment at the {{w|Lagrange point|L2 Lagrange point}}) from this flash, rather than the other way around. When the camera is taking a picture, the comic shows a totally dark shadow behind the shield.

The comic also has the camera making a "click" sound. In traditional mechanical cameras, this sound comes from the {{w|Shutter (photography|shutter}} opening and closing, and digital cameras mimic this sound so the user (and subject, when human) knows when the picture is being taken. JWST won't actually click -- it doesn't have a shutter, it takes long exposure digital images, and in space no one can hear you click.

The telescope also tells the universe to smile for the picture. The universe doesn't have a mouth to smile with {{Citation needed}}, although there are a number of features on Solar System objects that look like faces; this is a phenomenon called {{w|pareidolia}}. The most well known is the Man in the Moon, but there are [https://www.universetoday.com/121551/faces-of-the-solar-system/ numerous others].

The title text suggests that, due to the sunshield not being angled toward Mars, its surface has been badly scarred by the flash. This implies ''incredible'' strength of the flash, perhaps to ensure the light can return from its destinations, comparable to {{tvtropes|KillSat|death-ray satellites}} in fiction.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[The James Webb Space Telescope is floating through space, a black background.]
:JWST: Okay, universe-
:JWST: Smile!

:JWST: ''Click''

:[A bright flash glows from the telescope, turning most of the panel white. The left side is blocked and kept dark by the telescope's sunshield.]

:Caption: Astronomy fact: The purpose of the JWST sunshield is to protect the Sun and the Earth from the telescope's powerful flash.

{{comic discussion}}
[[Category:Telescopes]]