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title

LSAT - Low Signal Acquisition and Tracking

short description

LSAT is a phased array antenna for UHF SATCOM, capable of both direction finding and communication with small, low-power ground terminals.

Bio


Introduce yourself or your team

Hugo Shelley is the founder and lead designer at Iota Technology, an innovation consultancy and hardware development studio in London. He studied Physics and Philosophy at Oxford and completed his postgraduate studies at the University of St Andrews, Scotland. He spends his time helping tech startups make the leap from dreams to reality.

Catalin Edu graduated from Coventry University as an industrial designer and has been designing products for companies all over the world for the past 6 years. His designs include those for the marine (Raymarine), military (FLIR), and scientific equipment industries (Oxford Instruments), in addition to a wide range of consumer electronics. His main interests are IoT and the space industry.

Fereshteh Abbasi is a telecommunications engineer specialising in antenna design. She received her PhD in Electrical and Systems Engineering from the University of Pennsylvania in 2015. Since then she has actively been involved in research and development in the satellite communication industry.

Dani Epstein is a product designer specialising in photorealistic product renders as well as 3D printing and embedded electronics. He has extensive knowledge and practical experience with most commonly used manufacturing processes and has held down more jobs than he cares to recall, giving him an unusually broad work experience and peculiar skill set.

What makes you an ideal candidate for this Challenge?

Our little international team is extremely diverse! We come from a wide variety of backgrounds, both geographically and culturally. We’re united by an enthusiasm for space travel and innovation, and our excitement about the possibilities that cubesats represent for science and technology.

Hugo and Dani have worked on previous competitions together, while Edu and Fereshteh bring new skills to the team that were needed to make this project a reality.

LSAT is a synthesis of RF engineering & mechanical design - with some origami thrown in. Between us we cover all the disciplines necessary to put together this proposal. Given a little more time, we could even build it - we’re just missing a large, liquid-fuelled rocket to put it into orbit. Perhaps you can help …

Solution


Describe your solution.

LSAT is a high-gain, dynamic phased array antenna for UHF SATCOM. It features four hexagonal antennae that fold up into the solar panels as shown in the video demo here: https://youtu.be/UfuUwajlvcU

The array can track co-operative targets, enabling high speed communication with small, disadvantaged terminals such as handheld radios, unmanned ground sensors and emergency beacons. It can also operate in direction-finding mode, using beamforming and Doppler processing techniques to determine the precise origin of UHF signals.

Each antenna is an open-ended quadrifilar helix, made of copper traces bonded to a single sheet of dielectric film. The sheet is is stiffened with six fibreglass panels and formed into a hexagonal tube. The tubes fold flat into the space at the sides of the satellite and deploy using standard spring hinges.

The antennae feature 20Mhz bandwidth at UHF military uplink frequencies and may be operated at a higher downlink frequency with the use of a duplexer. Our simulation predicts almost 7dB of gain for the array, a fivefold increase in gathering power over a standard UHF tape-spring antenna.

By adjusting the phase of the signal at each antenna, the direction of the main beam may be rapidly changed without physically moving the satellite. This allows us to keep the beam locked on to a mobile or static target as the satellite passes overhead, providing horizon-to-horizon communication to even the smallest ground terminals.

The LSAT system is incredibly versatile. Using standard flex-rigid PCB manufacturing processes it is possible to print and test a new conductive element without modifying either the support structure or the method of deployment. L-band, S-band or higher frequencies are all possible. With only minor modifications it can be mounted on both 3U and 6U cubesats, including the 1.5U payload structure supported by the Prometheus cubesat bus.

What is the size of your proposed solution?

When stowed, each antenna and accompanying solar panel fold up with an overall dimension of 80 x 260 x 4.5mm, within the extra space at the sides of the cubesat allowable by the Cal Poly standard. The antenna itself occupies an estimated volume of only 15 cubic cm in a compressed state, expanding to 30 times this volume when deployed.

The accompanying UHF radio and array driving circuitry should take up no more than 0.5U of payload space and may be positioned anywhere in the body of the cubesat. The central aperture of the satellite remains unobstructed, providing a clear view for other payloads including earth-facing sensors.

The system is not limited to nadir-pointing cubesats (as illustrated) neither is it limited to arrays with only four elements. Solar panels that are hinged along the length of the cubesat provides scope for multiple, shorter hexagonal antennae to be deployed along the length. This is suitable for cubesats with a flight vector parallel to their longest side.

Does your solution help Special Operations Forces missions? How?

There are four main applications of this technology to Special Operations Forces missions:

1. Handheld SATCOM
LSAT’s high-gain antenna can form a stable link with small, handheld radios. The calculations in the attached PDF demonstrate that a robust communication link is possible with a ground terminal EIRP of only 7dBW, well within the capabilities (and safe limits) of a handheld radio.

A small cubesat constellation could operate as a backup in the event that the primary (MUOS) manpack radio fails or for missions that require ultra-lightweight equipment. These radios could also be issued to local (non-military) personnel for support purposes or humanitarian use (disaster recovery etc) providing a channel for communication where there may be no cell service available.

2. Unattended Ground Sensors

The high gain and beamsteering capability of the LSAT array make it idea for capturing data from unattended ground sensors in remote areas. As the satellite passes overhead, it dynamically changes the direction of the beam to ensure the strongest possible communication link. This minimises the power needed to communicate with the satellite, dramatically improving both the battery life of the sensor and quantity of data that can be collected.

The calculations in the PDF demonstrate that a 25kb/s data link may be achieved even at low satellite elevations. With an average pass time of 180s, it is possible to collect up to 0.5MB of data on a single pass. Under normal use (~30 kilobytes per day), a sensor may last for over 1 year on a single Panasonic 18650 battery. With light usage, many years of continued operation are possible.

3. Search & Rescue

The LSAT array may be operated in RDF (radio direction finding) mode. By using a combination of beamforming and Doppler processing techniques it is possible to determine the angle of arrival of UHF transmissions, and therefore their point of origin on the ground. This technique may be used to locate a standard-issue radio or specialised distress beacon.

4. Threat detection

RDF mode may also be used to locate the source of potential threats including jamming stations, UHF radar, areas of interference, etc. A constellation of cubesats could extend spectrum coverage if needed.

Where known, identify platform accommodation requirements for power.

The radio and driving circuitry will consume an estimated 0.1W in standby and 0.5W in receive. System power during transmission may be anywhere from 4-10W depending on the desired link budget. The average power consumption per orbit will depend on the mode and frequency of use.

LSAT provides scope for solar cells to be positioned on the reverse of the array, compensating for the power required by the radio and increasing the overall power budget for the cubesat.

Where known, identify platform accommodation requirements for thermal control.

LSAT requires no additional thermal control measures beyond those required for a normal UHF radio. To aid with thermal distribution, the satellite may spin slowly around the z-axis without affecting any of the the primary functions.

Where known, identify platform accommodation requirements for data transfer rate.

LSAT can cover its own telemetry requirements with data rates of up to 250kb/s.

Where known, identify platform accommodation requirements for data transfer volume (per orbit).

Data transfer volume per orbit depends on the mode of use. With over 1MB of data transfer possible per pass, the LSAT system should be able to provide general cubesat telemetry in addition to the requirements of most payloads. If additional data transfer is required, an S-band patch antenna may occupy the central (earth-facing) aperture of the satellite.

Where known, identify platform accommodation requirements for bus stability and attitude control.

After launch the cubesat must be successfully detumbled and oriented so that the z-axis points towards the earth. LSAT’s beamsteering abilities allow it to automatically compensate for 5 degrees or more of pointing innaccuracy.

Can you identify any additional platform accommodation requirements for your solution?

To accurately calculate the origin of a UHF signal we must know the orientation of the cubesat and its position relative to the ground. A GPS radio is essential, and star tracker(s) are recommended.

Can your concept can be implemented with current state-of-the-art flight-qualified components, or will it require additional development? Please describe.

It should be possible to adapt an existing flight-qualified radio with the necessary array driving circuitry. The antenna itself may be assembled using standard flex-rigid PCB manufacturing techniques, elevating it to TRL 3 within only a few weeks. All other necessary components including the solar panels, spring hinges and burn wire deployment mechanism may be selected from previously existing components at TRL8+

Intellectual Property: Do you acknowledge that this is only the Concept Phase of the competition, and all ideas are to remain the property and ownership of USSOCOM for future discretionary use, licensing, or inclusion in future challenges?

Yes

Supporting PDF upload

LSAT_presentation.pdf

comments (public)

  • Vasileios P. Nikolopoulos Nov. 20, 2017, 1:26 a.m. PST
    Dear Hugo,
    I have been reading carefully about all your Achievements! Really I was surprised. I think that it is a great work.
    I am sure it is interesting, and probably will help the people.
    Did you participate in Space Poop Challenge?
    I can't make any more comments.
    My best wishes and good luck to you and the Team too.
    Best regards
    Vasileios P. Nikolopoulos
  • Teodor Foca Nov. 15, 2017, 11:20 a.m. PST
    Thank you for your invitation for commenting. Yah, it looks nice and probably functional, from all the description I read. I am not an expert in telecommunication science and because of this handicap i have, i could not understand a part of the project. Probably some fancy 'new' radio transmitting technology that i am not aware of, and i didn't research for it either. But is good that you mention it. I will google for it somewhere in the near future.
    As a curious mind that i always had(and annoyed the hell out of some), i could not abstain to stumble over a certain problem. It is a strategical problem i suppose. You mention all the fancy radio telecommunication (LSAT,l-band,s-band,etc) capability, and the range of it looks functional to call back and forth (ground and 2000km altitude (LEO)), and it have enough survive chance - 1year for the battery you said somewhere, and the other gizmos that enhance it to be as practical as possible. Right? Right. And all of this for 1 single satellite? And is doing everything that needs to be done by himself alone? Then why the 'constellation' of satellites? (realistic, probably will be not more than a couple of tens order -like 10 or 20, anyway). You see my point? Why doing the same job by more than one? Is something not yet clarified? You need more to boost the signal or something? Again, excuse my curiosity, and as i already specified, some telecommunication skills i don't have them. Maybe a good reason exist somewhere, but you failed to mention it in the description - this is a good time to correct it i suppose.
    Overall, I have nothing to comment - it looks professional enough from the description you handled. I am a skeptic, and seeing is believing in my book of life rules. Yah, I want to see or hear about this satellite while in action. Until then, i wish you good luck !
    • Hugo Shelley Nov. 16, 2017, 2:24 p.m. PST
      Thanks for the questions! There’s a concept design for what a handheld CubeSat ground terminal would look like on page 6, but because the competition was to design the satellite payload itself (rather than anything on the ground) we didn't go into much detail here.

      What we did manage to show was that LSAT's high gain antenna was able to compensate for the very low gain antenna on the handheld, enabling the two to talk to each other.

      That’s tricky, because handhelds can’t transmit at extremely high power - if they do, you drain the battery and potentially harm the operator as well! So what we’ve shown is that it’s possible for a handheld radio to be used safely, and to last for a sensible mission duration.

      You’re right that there’s a lot of potential for this technology beyond USSOCOM. One of the drawbacks of placing your cubesat in space is that ground stations can be expensive and this limits the appeal for schools and universities. This technology allows us to communicate with cubesats quickly and easily, and with surprisingly high data rates.
    • Teodor Foca Nov. 16, 2017, 3:25 p.m. PST
      So, your technology is using the ground stations in between LSAT and specialized transmitter.
      I really was hopping your LSAT ,transmit to/receive from, ground device. I am not that much into telecommunications - maybe i should. :)
      So you build only the antenna... ok, i suppose now you have to build the actual satellite. No? Go to work!
      or... you can call/email a company that have the satellite/ or custom make it for you. In america everything should be possible, if you are there! If you are not in america, you're screwed. :))

      You are on the wave - the hard thing is to stay on it until the project is finished. Something that should help you - [plan ahead!] - and by that i mean: - what to construct next? what to concentrate next? what is imperative and urgent? priorities! who to call, who to contact, who to add to my team? etc - just write it down and try to follow the plan of todo's. I do it for very hard stuff myself too(but very rarely), and is working for me. I feel this is a hard period/project for you.

      I give you something to think for? to plan for? so far, in ALL this discussions? I hope i was of any help.
      I really wish you all the good luck!
    • Hugo Shelley Nov. 16, 2017, 3:41 p.m. PST
      LSAT transmits directly to the handheld device (i.e. the handheld device *is* the ground terminal). Sorry if I wasn't clearer!

      We're based in London but there are a few companies in Europe who supply CubeSat parts, some of which we have suggested. But you're right that the focus was to design the antenna - the other supporting parts are just to demonstrate how you might fit everything together, and I know that USSOCOM have their own cubesat bus that they will be using.
    • Teodor Foca Nov. 16, 2017, 4:41 p.m. PST
      What is your specialty? (in the pdf says system designer but i want something more specific than that).
    • Hugo Shelley Nov. 18, 2017, 5:23 p.m. PST
      I specialise in electronic hardware development.
  • Henry Duran Nov. 15, 2017, 11:18 a.m. PST
    It can be an appropriate option for a correct efficiency considering the cost
  • MrHardNails Nov. 14, 2017, 2:39 a.m. PST
    Love the practicality and efficiency of intended range for in field communication requirements, i also see that people are concerned about the environmental exposures regarding "Micrometeorite" impacts and degradation of panels and possible tearing, however i think turbulence derived from gravitational affects and weather might be more of a concern as per the altitude being below 700 km.
    • Hugo Shelley Nov. 15, 2017, 1:50 p.m. PST
      Thanks for your comment! There's not too much weather up there. The occasional air molecule that will eventually cause the satellite to de-orbit, but it takes time for that to happen.
    • MrHardNails Nov. 15, 2017, 3:02 p.m. PST
      Agreed, i wasn't having the best day when i replied concerning the weather so to speak :(, i feel so intelligent, next time i will keep my brain mouth/keyboard filter in check, sincerely its a affordable and practical solution so well done from me Jacques Louie van der Merwe
  • Dirk Patze Nov. 13, 2017, 10:40 p.m. PST
    Concerning the antenna arms: Have you estimated the thermal stress and the aggressive space conditions in your calculations? I wonder how long this fold out array is estimated to last concerning the time you want the satellite to provide its service. How resilient is it concerning micrometeorite impact, as increased surface means increased risk?
    • Hugo Shelley Nov. 15, 2017, 1:52 p.m. PST
      The hexagonal arms are mostly structural. For a micrometeorite to have an effect it would have to cut straight through one of the copper antenna traces. Or rather, you'd need a series of micrometeorites in a neat line to cut through it. If you'd ever played one of those fairground games where you have to shoot out the ace from a playing card then you know how difficult that is!
    • Dirk Patze Nov. 15, 2017, 11:26 p.m. PST
      Good explanation! I was just wondering as I only found 'custom' in the document concerning the frame.
  • William Newton Nov. 13, 2017, 2:12 p.m. PST
    How is it positioned or re-positioned? What is it's earthly range to connect? With low orbit earth space getting crowded, would this be a problem for deployment?
    • Hugo Shelley Nov. 13, 2017, 3:47 p.m. PST
      Thanks for the questions! The satellite can be positioned using the reaction wheels inside the MAI-400 at the top of the satellite. The antenna allows full horizon to horizon coverage - that's a maximum 2574km of path distance between the satellite and the ground terminal! Crowding isn't a problem, as we fly at ISS altitude, below the congested 700-1000km region. That also ensures that the satellite will be well below the 25yr guideline for maximum operational life.
    • William Newton Nov. 13, 2017, 4:03 p.m. PST
      Thanks, could you explain the reaction wheels?
    • Hugo Shelley Nov. 13, 2017, 4:30 p.m. PST
      The reaction wheels are part of the MAI-400, which is an ADCS (attitude control and determination system) manufactured by Maryland Aerospace. It's not a core part of our design, just a supporting part. SOCOM will most likely be looking to use their own ADCS for their missions.

      Reaction wheels are just spinning discs. By changing the rate at which they spin, it's possible to rotate the spacecraft.
    • William Newton Nov. 13, 2017, 4:50 p.m. PST
      Cool
  • Vaibhav Rahangdale Nov. 12, 2017, 7:25 a.m. PST
    Really amazing dude ....hats offff !!!
  • Alex Rubey Nov. 11, 2017, 6:46 p.m. PST
    It's a great design, and I'm for it considering it's backup communication ability, and in the future I think that micro satellites like this should also be deployed to replace the aging civilian GPS architecture
  • IVader Komarov Nov. 9, 2017, 5:47 a.m. PST
    Nice design
  • sunny odina Nov. 9, 2017, 5:33 a.m. PST
    Marvellous! especially if this can be fully monitored from earth 24/7.