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A satellite engineer explains the basics of space electronics

blog.snapeda.com

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Re: A satellite engineer explains the basics of space electronics

#11

Post by sandworm101 »

awake wrote: post #8
sandworm101 wrote: post #5

I read so many stories about companies with new ideas for satellite internet. But i am visiting my parents next weekend. Their house is off grid in rural BC. They only have one internet option: a dish pointed to a geostationary sat which I will no doubt have to repoint on saturday. They pay insane rates for practically no bandwidth. There is only the one company: explorenet. When exactly are any of these innovations…

Checkout starlink the satellite network being created by spacex. Here is a good FAQ https://www.reddit.com/r/Starlink/comments/7zqm2c/starlink_f...

Great, but while i see lots of talk of this for ships and planes i've seen not a single file or application from spacex to become a residential provider anywhere, much less in canada. So they remain perpetually 10+ years away.

Re: A satellite engineer explains the basics of space electronics

#12

Post by gammatrigono »

sandworm101 wrote: post #11
awake wrote: post #8

Earlier quoted context omitted.

Checkout starlink the satellite network being created by spacex. Here is a good FAQ https://www.reddit.com/r/Starlink/comments/7zqm2c/starlink_f...

Great, but while i see lots of talk of this for ships and planes i've seen not a single file or application from spacex to become a residential provider anywhere, much less in canada. So they remain perpetually 10+ years away.

https://www.fcc.gov/document/fcc-authorizes-spacex-provide-b...

Residential service filing probably (!) appears on the priority list after launching the 4-12,000 satellites into LEO.

Re: A satellite engineer explains the basics of space electronics

#13

Post by dghughes »

I'm surprised electronics work on the earth.

Such fragile things it's amazing how little it takes to destroy a device. And how much energy can be put through the same fragile device.

And how much energy is in one Coulomb. The example I like is two points each with one Coulomb repel with a force of one millions tons.

A recent artie I read spoke about the reaction wheels of old spacecraft failing. Solar flares caused arcing in the metal ball bearings the would pit the bearing race. So if a steel ball bearing can't take it imagine fragile electronic devices.

Re: A satellite engineer explains the basics of space electronics

#14

Post by irq-1 »

Here's an interesting paper that discusses some design issues.

https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7086415

> To mask the effects of upsets in the FPGA configuration memory, temporal or structural redundancy can be applied to the system. Temporal redundancy involves the replication of a computation or logic function in time to mitigate failures that occur during one of the redundant computations. Structural redundancy involves the replication of selected circuit structures to remove single-point failures. Failures in the circuit can be masked by performing the logic or computing function in more than one circuit location.

> The most common form of structural redundancy is to apply triple-modular redundancy (TMR) [24]. As shown in Fig. 6, TMR involves the triplication of all circuit resources and the addition of majority voters at the appropriate circuit outputs.

Re: A satellite engineer explains the basics of space electronics

#15

Post by walrus01 »

sandworm101 wrote: post #5

I read so many stories about companies with new ideas for satellite internet. But i am visiting my parents next weekend. Their house is off grid in rural BC. They only have one internet option: a dish pointed to a geostationary sat which I will no doubt have to repoint on saturday. They pay insane rates for practically no bandwidth. There is only the one company: explorenet. When exactly are any of these innovations…

Without asking too much detail, approximately where is there house? Is there any chance there is a regional WISP they could get service from?

In general, consumer grade VSAT service via geostationary satellite should be a last resort, if anything else is available. The economics of launching 5000 kilogram satellites into geostationary orbits mean that transponder kHz in Ku/Ka-band spot beams need to be significantly oversubscribed.

The actual cost of satellite capacity, translating dedicated (1:1 ratio) Mbps into transponder capacity, plus the cost of running earth stations on the ISP uplink side, can range from $1800 to $5500 per Mbps per month.

In order to make any money at all off a large number of $100 to $150/month consumer grade VSAT services it needs to be radically oversubscribed.

Xplornet has a particularly bad reputation as an ISP in general, which doesn't help.

Things like SpaceX's starlink or other upcoming LEO/MEO services like Oneweb are promising. But not available yet.

Point to multipoint wireless last mile via 2.4/3.5/3.65/5.2/5.8 GHz bands can be much more effective. It's even possible for WISPs to offer 75 Mbps x 25 Mbps packages based off the latest Ubiquiti 802.11ac gen2 platforms, Cambium PMP450 or Mimosa A5 AP radio platforms.

Disclaimer: I work in both satellite Internet and point-to-point/point-to-multipoint microwave and millimeter wave.

Re: A satellite engineer explains the basics of space electronics

#16

Post by walrus01 »

sandworm101 wrote: post #11
awake wrote: post #8

Earlier quoted context omitted.

Checkout starlink the satellite network being created by spacex. Here is a good FAQ https://www.reddit.com/r/Starlink/comments/7zqm2c/starlink_f...

Great, but while i see lots of talk of this for ships and planes i've seen not a single file or application from spacex to become a residential provider anywhere, much less in canada. So they remain perpetually 10+ years away.

It is much more likely that it will be economical to use in a similar method to o3b, to bring a decent amount of capacity to a single location (example: totally isolated very rural valley somewhere in northern BC), and then distribute bandwidth from there.

The link budget problems for gain and EIRP, and cost of CPE, may make it cost prohibitive to put individual CPEs on peoples' roofs as a competitor to last mile WISPs.

I can see a scenario where a WISP buys a $7000 to $15000 dual-antenna terminal and a monthly recurring service package in the $700 to $1200/mo range, for a decent chunk of semi-dedicated capacity, and then redistributes access from there.

For those who want to understand how this works, o3b at MEO works on the same general concept, but at a more expensive and high bandwidth scale. It's been operational for years now. There's lots of good reference material out there on O3B.

Take the same two-satellite make-before-break handoff system used by o3b and apply it to a much larger number of LEO satellites, and smaller terminals, that's the general idea of how oneweb and starlink are intended to work.

Re: A satellite engineer explains the basics of space electronics

#17

Post by snowwindwaves »

sandworm101 wrote: post #5

I read so many stories about companies with new ideas for satellite internet. But i am visiting my parents next weekend. Their house is off grid in rural BC. They only have one internet option: a dish pointed to a geostationary sat which I will no doubt have to repoint on saturday. They pay insane rates for practically no bandwidth. There is only the one company: explorenet. When exactly are any of these innovations…

We get satellite internet from Infosat also in BC. It's not cheap either though.

Re: A satellite engineer explains the basics of space electronics

#18

Post by StavrosK »

dghughes wrote: post #13

I'm surprised electronics work on the earth. Such fragile things it's amazing how little it takes to destroy a device. And how much energy can be put through the same fragile device. And how much energy is in one Coulomb. The example I like is two points each with one Coulomb repel with a force of one millions tons. A recent artie I read spoke about the reaction wheels of old spacecraft failing. Solar flares caused a…

You're looking at it the wrong way. Electronics work on earth by definition, as that's where we want them to work. You can be surprised that electronics can be made so fragile and still work on earth, but being surprised they work is begging the question.

Re: A satellite engineer explains the basics of space electronics

#20

Post by pseudobry »

lizknope wrote: post #10

I've been designing semiconductors for 20 years and I thought I would learn something but this article said nothing other than he wished there were more radiation hardened devices out there. You can learn more from wikipedia than this article. https://en.wikipedia.org/wiki/Radiation_hardening

I have not been designing semiconductors for 20 years and I thought I would learn something...and I did!
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