Comments on: First Light for DSOC! https://habitablezone.com/2023/11/24/first-light-for-dsoc/ Tue, 07 Apr 2026 04:45:30 -0700 hourly 1 http://wordpress.org/?v=3.3.1 By: RL https://habitablezone.com/2023/11/24/first-light-for-dsoc/#comment-52707 RL Thu, 30 Nov 2023 18:04:07 +0000 https://habitablezone.com/?p=101936#comment-52707 While large, that is VASTLY smaller than the rf dish would have to be for the data rate it will provide... While large, that is VASTLY smaller than the rf dish would have to be for the data rate it will provide…

]]> By: RL https://habitablezone.com/2023/11/24/first-light-for-dsoc/#comment-52706 RL Thu, 30 Nov 2023 06:10:32 +0000 https://habitablezone.com/?p=101936#comment-52706 When you have one terminal in space, and one on the ground you can greatly minimize the size weight and power required by the space terminal by increasing the size weight and power on the ground, where doing so is 'cheap'. For instance, doubling the diameter of the ground terminal reduces the power the space terminal needs to transmit by a factor of 4. Quadrupling the laser power on the ground allows the diameter of the space terminal by a factor of 2. High power space-qualified lasers are NOT easy to find- I don't think any lasers of the type we need have been space-qualified for laser powers over 10 Watts. So you can really offload a lot of the cost and difficulty by increasing the size and power of the terminal on the ground- where its easier. For the relay you propose you would need to launch a pretty large telescope VERY far away... We have demonstrated we can close a link even when the target is located ~3degrees away from the sun in the sky... the same restriction we have for RF. Maybe with improved optical filter technology we can get even closer to the sun. Yes, it would be nice to have such a relay, but it would be VERY expensive- we haven't even done it for RF communications yet. When you have one terminal in space, and one on the ground you can greatly minimize the size weight and power required by the space terminal by increasing the size weight and power on the ground, where doing so is ‘cheap’.

For instance, doubling the diameter of the ground terminal reduces the power the space terminal needs to transmit by a factor of 4.

Quadrupling the laser power on the ground allows the diameter of the space terminal by a factor of 2.

High power space-qualified lasers are NOT easy to find- I don’t think any lasers of the type we need have been space-qualified for laser powers over 10 Watts.

So you can really offload a lot of the cost and difficulty by increasing the size and power of the terminal on the ground- where its easier.

For the relay you propose you would need to launch a pretty large telescope VERY far away…

We have demonstrated we can close a link even when the target is located ~3degrees away from the sun in the sky… the same restriction we have for RF.

Maybe with improved optical filter technology we can get even closer to the sun.

Yes, it would be nice to have such a relay, but it would be VERY expensive- we haven’t even done it for RF communications yet.

]]> By: BuckGalaxy https://habitablezone.com/2023/11/24/first-light-for-dsoc/#comment-52690 BuckGalaxy Mon, 27 Nov 2023 20:30:02 +0000 https://habitablezone.com/?p=101936#comment-52690 All it would take is a satellite placed in solar orbit which could always see both Earth and Mars. I suspect the cost is not worth it given the short comm blackout and relatively small number of assets on Mars currently. But that will certainly change when people get there. All it would take is a satellite placed in solar orbit which could always see both Earth and Mars. I suspect the cost is not worth it given the short comm blackout and relatively small number of assets on Mars currently. But that will certainly change when people get there.

]]> By: podrock https://habitablezone.com/2023/11/24/first-light-for-dsoc/#comment-52679 podrock Sun, 26 Nov 2023 05:41:05 +0000 https://habitablezone.com/?p=101936#comment-52679 Nothing going up or down because the sun is in the way. Has there been any thought to a relay satellite to avoid this in the future? RL, will this device be planned as a satellite as well? Maybe throw some up in mars's L points? Nothing going up or down because the sun is in the way. Has there been any thought to a relay satellite to avoid this in the future?

RL, will this device be planned as a satellite as well? Maybe throw some up in mars’s L points?

]]> By: RL https://habitablezone.com/2023/11/24/first-light-for-dsoc/#comment-52678 RL Sun, 26 Nov 2023 03:24:19 +0000 https://habitablezone.com/?p=101936#comment-52678 The Laser Communications Relay Demonstration is a relay at GEO, ILLUMA-T is a laser terminal just put on the ISS- it will send ISS data up to LCRD in GEO and then LCRD will relay it to the ground at 1.2Gbps. The Laser Communications Relay Demonstration is a relay at GEO, ILLUMA-T is a laser terminal just put on the ISS- it will send ISS data up to LCRD in GEO and then LCRD will relay it to the ground at 1.2Gbps.

]]> By: BuckGalaxy https://habitablezone.com/2023/11/24/first-light-for-dsoc/#comment-52677 BuckGalaxy Sun, 26 Nov 2023 02:34:03 +0000 https://habitablezone.com/?p=101936#comment-52677 I imagine at some point relay communication satellites in geo, solar orbit or at some lagrange points could be stationed to get around that problem. I imagine at some point relay communication satellites in geo, solar orbit or at some lagrange points could be stationed to get around that problem.

]]> By: RL https://habitablezone.com/2023/11/24/first-light-for-dsoc/#comment-52675 RL Sat, 25 Nov 2023 20:47:36 +0000 https://habitablezone.com/?p=101936#comment-52675 Depending on how long its out of line of sight the error correcting codes might be able to let you ride through it, worst that will happen is you lose the connection entirely and have to start the acquisition process again. The odds of such an interruption by a plane are vanishingly small but clouds are an issue. We need cloud free line of sight. This is where RF does have an advantage- clouds are not a serious issue for RF. We solve that by putting multiple ground terminals in different geographic locations that are not correlated in weather. So if one is clouded out then we have others to use. Depending on how long its out of line of sight the error correcting codes might be able to let you ride through it, worst that will happen is you lose the connection entirely and have to start the acquisition process again.

The odds of such an interruption by a plane are vanishingly small but clouds are an issue. We need cloud free line of sight. This is where RF does have an advantage- clouds are not a serious issue for RF. We solve that by putting multiple ground terminals in different geographic locations that are not correlated in weather. So if one is clouded out then we have others to use.

]]> By: BuckGalaxy https://habitablezone.com/2023/11/24/first-light-for-dsoc/#comment-52674 BuckGalaxy Sat, 25 Nov 2023 19:43:16 +0000 https://habitablezone.com/?p=101936#comment-52674 Light based communications with a narrow receiver. Is it more likely there will be data interruptions or even data loss from objects blocking the direct line of communications? How narrow is the communication band? Agree with Pod, excellent work you're doing! Light based communications with a narrow receiver. Is it more likely there will be data interruptions or even data loss from objects blocking the direct line of communications? How narrow is the communication band?

Agree with Pod, excellent work you’re doing!

]]> By: RL https://habitablezone.com/2023/11/24/first-light-for-dsoc/#comment-52673 RL Sat, 25 Nov 2023 18:21:12 +0000 https://habitablezone.com/?p=101936#comment-52673 Contrast that with the 18 meter RF dishes used to receive transmissions from the moon. In the Lunar Laser Communications Demonstration the ground receiver was four 40cm telescopes. The space transmitter was a 10cm diameter telescope transmitting 0.5 Watts of laser power. That was able to transmit 622 Mbps - the highest data rate yet achieved from the moon. We are building the terminal we are working on to do transmit and receive. The transmit will consist of four 15cm diameter off-axis parabolic telescopes. Each capable of transmitting up to 20 Watts. Contrast that with the 18 meter RF dishes used to receive transmissions from the moon.

In the Lunar Laser Communications Demonstration the ground receiver was four 40cm telescopes. The space transmitter was a 10cm diameter telescope transmitting 0.5 Watts of laser power. That was able to transmit 622 Mbps – the highest data rate yet achieved from the moon.

We are building the terminal we are working on to do transmit and receive. The transmit will consist of four 15cm diameter off-axis parabolic telescopes. Each capable of transmitting up to 20 Watts.

]]> By: podrock https://habitablezone.com/2023/11/24/first-light-for-dsoc/#comment-52671 podrock Sat, 25 Nov 2023 04:31:54 +0000 https://habitablezone.com/?p=101936#comment-52671 Is it receive only? Damn fine work RL Is it receive only?

Damn fine work RL

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