> JWST is transmitting data back to Earth on a 25.9-gigahertz channel at up to 28 megabits per secon
0.028*3600 = 100 Gbit/hour
No problem here.
0.028*3600 = 100 Gbit/hour
No problem here.
The issue isn't so much blackout (the segments are 120 degrees separated^), but that contact time is expensive and you don't get 100% of the uptime to yourself. The DSN is basically the only infrastructure we have for this sort of long range communication. There are only three stations and JWST is sharing time with a bunch of other missions including everything that's currently on Mars. Scheduling takes place far in advance.
The problem also isn't absolute storage space onboard, even if capacity degrades at a gig a year, it's whether you can drain it faster than you fill it. That said, there is likely to be some limit on hard drive space depending on what the current rad hardened solutions are. JWST is built on very robust and well-known hardware that has good provenance in space. For a LEO mission you might be willing to risk less tolerant components to get terabytes of capacity, but out there you want extremely resilient components and 68 GB is probably the balance. Sentinel 2 (an ESA Earth observation satellite) has 2.4Tb/300GB onboard for example.
Ultimately the missions planners budget for how much data they're allowed to stream back and they've figured out an amount that is acceptable.
But in general, yes. If you can write to a disk and ship it, that's a good solution. IceCube (South Pole) generates TBs of data. We send back 0.5 TB of critical data every month over a fast satellite link, crucial alerts and telemetry are sent over Iridium (24/7 avail) and the rest gets sent back to Madison (WI) on a plane each summer.
^ In theory this means that you can service three missions at a time though, if they're not all in the same direction.
That said, NASA have been expanding the DSN for the past decade with four new antennae added so far (remaining two expected by 2025), it's just slow progress as usual with most of what they do lately. DSN antennas don't bring in jobs (and thus votes) for senators the way decades long flagship projects like JWST or SLS do.
There are 3 DSN complexes, but each complex has multiple dishes. One station is very frequently talking to multiple spacecraft at once.
Reading the article further, I was sort of surprised there’s only 68 GB of solid state storage on board. Does anyone know if that’s considered very large for space-grade systems?
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.
You forgot the units.
0.028 Mb/s *3600s = 100 Gb/hour = 12.6 GB/h