onetwentythree

Here’s a concept out of APL, but as far as I know it is not getting much traction yet.

https://interstellarprobe.jhuapl.edu

The 90% efficiency of the wireless transmission would be on top of the efficiency of typical charging (which is mostly losses after the power reaches the vehicle).

Yes, but remember they are very different telescopes for different types of astronomy. Roman is a survey telescope with a wide field of view, designed to discover new objects, etc. JWST has a large aperture and narrow FOV to get the closest look possible at specific targets identified in advance. They will compliment each other well.

To provide more information than the others who responded: typical sprinkler systems are not automatically activated in response to a fire alarm. Each sprinkler head has a small glass vial filled with a liquid, calibrated to break at a certain elevated temperature (e.g 160 or 180 F). The flow of water starts when the glass breaks. So there has to be a significant fire near the sprinkler before it activates.

One weakness is that the glass vial is fragile. In some hotels you’ll see signs reminding guests not to hang clothes from the sprinkler head, as a clothes hanger could break the vial and activate the water flow.

You can get multi-turn absolute encoders for these applications.

I don’t think they’re in trouble for missing the deorbit target.

The concern is that the second stage didn’t perform as expected. What if that affects the primary mission on the next flight? They need to understand the root cause before they fly again.

As the article states, the upcoming Europa Clipper launch requires an upper stage relight to put the spacecraft on the desired trajectory. If the second burn does not go as expected, the mission could be in jeopardy.

That only applies to linear regulators.

The router on this page uses a switching regulator. Switching regulators have a relatively constant power draw over the entire input voltage range.

Not sure about a mission as old as voyager, but most modern missions use CCSDS protocols, which are open and available online.

But just because you know the protocol dues not mean you have enough information to send a valid command. The commands are wrapped in a common protocol, but the commands themselves are typically mission-specific and definitely not made public.

Here’s an example of someone unaffiliated with the mission decoding JWST telemetry. While they were able to identify the packets defined per CCSDS protocols, they do not know the actual content of the packets, which are mission specific.

https://destevez.net/2021/12/decoding-james-webb-space-teles...

And as someone else mentioned, the biggest hurdle with getting a command to voyager is access to a 70 m dish. Not many of those floating around…

The shock typically comes from the release of the preload, not from the NEA itself.

Maybe I’m wrong, but having it classified as a planetary mission probably funds their positions and a lot of continued research (even if the research is based on data already taken). Reclassifying the mission probably means the scientists need to look for new sources of funding. So I get that they’re not happy, but it sounds like a rational decision on NASA’s part.

It uses NASA’s Deep Space Network. There are three stations around the globe (California, Australia, and Spain), spaced so that there is near continuous coverage for deep space missions. JWST points it’s antenna at the station that is currently in view.

However, the ground stations are shared between many missions, so they are not available for JWST all the time. Expectation is that JWST gets 8-12 hours/day of DSN time.

I know this is a joke but...

JWST does not use a typical flash-based SSD. The mass storage is all SDRAM. There are layers of error correction and scrubbing to handle bit flips.

There are only 8 hours of downlink time per day. DSN resources are limited and shared among many missions.

Everything was sized based on the expected volume of data that the telescope would be able to take. The instruments only generatedata at a certain rate, and there are inefficiencies involved with slewing between targets. Having a larger recorder or faster downlink would not mean that JWST could take more science data.

The antenna is steered to point towards the DSN antenna on the earth. A larger moving mass would make it harder to maintain telescope pointing while the antenna is moving.

In reality, the antenna pointing is 'paused' during each science observation, unless pointing is needed due to the length of the observation.

There’s no way to mitigate the risk of statistically random meteorites that can come from any direction.

The primary mitigation is to use predictions of larger events, such as meteor showers, and move the observatory to an orientation that reduces the risk of damage.

There is no consumable liquid helium. Past space telescopes have used consumable coolant, but JWST has a closed refrigeration system to cool the one instrument that requires active cooling.

If all goes as planned, the limiting factor is propellant. And the propellant tanks have the ports for on-orbit refueling, in case there is ever a desire to develop a robotic servicing mission for the task.

Yes, that is being planned for, but I’m not sure if any cycle one proposals involve joint observations.

https://jwst-docs.stsci.edu/jwst-opportunities-and-policies/...

The spacecraft will make corrections with its onboard thrusters over the course of the mission.

Yes. Power supplies up to 60VDC are typically designed to fall under SELV and are considered intrinsically safe. SELV requires isolation and a single fault tolerant design. Here is some additional info:

https://www.edn.com/what-does-selv-mean-for-power-supplies/

I doubt the USB-C power negotiation feature is specifically a safety function, but as other comments have pointed out it makes the system even safer.

I haven’t looked at the spec, but I wonder if there is any functionality that prevents a power supply from applying 48V all the time. i.e. is it possible to deliver a functional charger that is not SELV and has no power negotiation?

Yes, you’re correct, but NASA is funding ~97% of the project. CSA and ESA each contributed a science instrument, and ESA is providing the launch. Otherwise, it’s all NASA.