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C🅰️tSE Profile picture
C🅰️tSE
@CatSE___ApeX___
Curios cat. 🅰️
In2r🅰️cing Profile picture 5 subscribed
Sep 24 • 9 tweets • 4 min read
BlueBirds have all flipped to radar cross section large.

They also exhibit this type of increase
in drag.

I conclude that detumbling was succesful and that the payload now consistently displays a large radar reflecting cross section towards earth.

Likely still inside the LVAs.
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Image BlueWalker 3 exhibited the same signature change of increased drag coefficient and a RCS flip 2022-10-06

~ Launch + 26 days.

The 5 BB1s are all there Launch +10 days.

Practice makes perfect.

2/n Image
Sep 21 • 8 tweets • 2 min read
Applications in all four phases.

Observe - sensor input
Orient - coms
Decide - more coms
Act - electronic warfare

Communications use cases but also non communications use cases.

The specs of a set of formation flying BB1 FPGAs makes them FF-SAR FoPen AKA FOLPEN capable.

1/n Things has molecules in them. They react to electromahnetic fields differently.

And you can add resolution/ signature by formation flying, by dual polarization and by large bandwidth.

AST does all of that. ✅✅✅👀

2/n
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Sep 15 • 8 tweets • 3 min read
Constellation level aggregated out of band emmission interference is a showstopper for Starlink.

This is due to crazy big leakage in adjacent bands/channels.

So when constellation increase from 300 to 4500 (15x) they need to cut radiated power down to 15%
The system can’t scale Image There is a term for such a system:

Non-scalable architecture. In technical contexts, this is often referred to as negative scaling or diminishing returns.

2/n
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Sep 14 • 5 tweets • 3 min read
Here are some Carrier to noise specifications of AST SpaceMobile.

In a filing today to the FCC Starlink reveals more of their d2c system.

Click link twice.

1/n licensing.fcc.gov/myibfs/downloa…



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Image Space-x Starlink d2c will drop from being able to do 5dB SINR (voice) to 0dB (texts)

If they were to comply with FCC rules.

We can now compare this to $ASTS.

2/n

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Sep 14 • 25 tweets • 8 min read
Scotia analysts apparenly read some of the DD shared by the SpaceMob community.

If You want Alpha or ”edge” investing in the nascent SCS market, so should You.

Previously thought by many to be the more technically advanced satcom operator Starlink is not getting approval.

1/n 🐾 ACLR. Adjacent Channel Leakage Ratio.

Recent requests by Starlink and some math (I was more kind to them than RKF engineering)

Is for Starlink ~-24.6 dBW/m2/MHz
And for AST ~-45 dBW/m2/MHz

This relates to quality of RF equipment.

A 20dB delta.

2/
Sep 2 • 22 tweets • 10 min read
A few aspects of a NTN system design affects the area spectral efficiency of the system.

I have touched on them and how they relate to Shannons law.

High directivity that creates narrow beams and small cells is key.
See my pinned tweet.

Then there is also interference.🧶🐈‍⬛ Image We can think of this as the area spectral efficiency aSE as the main metric by which MNOs will choose which Satellite Network Operator Mobile to work with.

And interference is the metric by which regulators select which SNO-Ms are allowed to operate at all.

Gain affects both
/2 Image
Aug 24 • 22 tweets • 12 min read
T-Mobile and a Freudian slip.

Decimation. What is that?

🧶🪓🐈‍⬛

Adhering to interference regulations of aggregate OOBE PFD limits would require a deficient system, such as Starlink d2c v2 mini, to use very wide guard bands and/or throttle (shrink) their power.

1/n
Image PCS spectrum block that Starlink and T-Mobile intends to use is very narrow to begin with this has a large impact.

They need to maximize its use in power and in bandwidth to make the system profitable.

If they do that with deficient / sub par technolgy it affects others.

2/n Image
Aug 17 • 46 tweets • 22 min read
Live view of @FCC regulatory staff watching recent Starlink and T-mobile filings asking to be exempt from new rules they helped greate and want to see imposed on others.

🧶🐈‍⬛

1/n
Image In 2020 T-mobile asked FCC not to allow ASTs system w/o filings to show that they do not cause harmful interference to terrestrial networks.

$TMUS also requested new rules that FCC started.

AST showed their system doesn’t cause interference. ASTS design criteria since 2018.
2/n


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Jul 26 • 11 tweets • 6 min read
Let’s unpack this $ASTS picture.

First and foremost 150+ heroes building revolutionary technology.

Many Thanks to the @AST_SpaceMobile staff.

🧶🐈‍⬛

1/n Image It is the same guys as in this picture from january.

But a few things have progressed.

Notice the evolved (as in much more simple & easy) contraption to furl an array on the left.

2/n
Jul 11 • 14 tweets • 8 min read
There was a meeting between FCC and AST SpaceMobile representatives on July 8th 2024.

What can we learn from the Ex Parte filing?

1/n


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Image ”The parties reviewed the current status of AST SpaceMobile’s unopposed amendment, filed on March 11, 2024, converting its Petition for Declaratory Ruling seeking market access to an Application to Launch and Operate under the jurisdiction of the United States (“Amendment”)2”
2/n Image
Jul 3 • 7 tweets • 2 min read
CatSEs li’l thread on risks and chance.

Did you know an AST BB block 2 has three seperate redundant Telemetry control links. (S-band, UHF and embedded in the Q/V feeder link).

Why this extreme 3x redundancy?

🎲🐈‍⬛

1/n Image If you consider success and failure as mutually exclusive dichotomy type entities

All is well v/s total failure.

Then you get:

Probability of succes = 1 - probability of failure.

I can re-label that as:

Chance% = 100% - Risk%

2/n Image
Jun 24 • 9 tweets • 7 min read
Looking at the antenna elements ( printed dual polarization dipole antenna) and the frequenzy used
(DMSP)

We could be looking at one of the ALT/dual use cases being an MPAR Multi-function Phased Array Radar (MPAR)

1/n


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Image What type of tricks might such an array be capable of?

Just like BlueWalker 2 was built in a reverse communications experiment there are more of those. One has an array here in Sweden.

2/n


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Jun 21 • 22 tweets • 9 min read
Might be a good time to compare AST SpaceMobile constellation to Space-X Starlink 2GHz VLEO.

🧶🐈‍⬛

1/n For Elon Musk financing his Mars transportation system needs to maximize payload to orbit.

For Abel Avellan designing an efficient system to connect the unconnected is the purpose drives him to keep total payload down.

2/n
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Jun 1 • 10 tweets • 6 min read
There are different portions of lowband spectrum that BlueBirds block 1 and BlueWalker 3 can use.

The range has public safety and commercial cellular spectrum in it.

🧶🐈‍⬛

1/n
Image Back in 2020 plan was 617-960 range. In 2024 the plan is 617-960 MHz range. Same.

Micron antenna elements are c-c 161 mm. That is optimized for ~930 MHz if You space the phased array at 1/2 wavelength.

Consistent with that range.

2/n
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Jan 3 • 25 tweets • 11 min read
Starlink v2 mini. Some performance measures. ”7Mb” (7mbps DL?) per cell

We can also compare gain levels:

Starlink v2mini 29–38dBi
BlueBird block2 40-47 dBi


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Image Unit economics of AST satellites.

Throughput per beam is in ASTs case (as in Elons) bandwidth dependent.

Just that AST gets much more of each MHz fronthaul due to much higher Area Spectral Efficiency. (Smaller cells and higher modulation).



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Dec 24, 2023 • 6 tweets • 4 min read
Starlink v2 design.

Some analysis.

40x40 (1600 antenna elements).
At ~8.8 cm spacing.
Seems optimized for ~1,700 MHz
(Midband / S-band)

For comparison BW3 / BB1 s are
90x90 Lowband elements.
At ~16.1 cm spacing.

1/n


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Image This has some implications.

The v2 mini will use spectrum with worse propagation charachteristics and larger atmospherical attenuation.

V2 will use a phased array that has fewer elements which means much wider beams and much lower directivity.

2/n
Apr 1, 2023 • 4 tweets • 3 min read
It was always 90 ASICs for global coverage. Adding 5 FPGAs is an increase. 🤦🏻‍♂️

Then 110 (115 counting FPGAs) for global MIMO. And so on.

🤡/n ASTS has been refining their beamforming tech for two years using BlueWalker2 talking to BlueWalker 1. AND they do mention beamforming on the call.

🤡🤡/n
Apr 1, 2023 • 5 tweets • 3 min read
$ASTS Lets talk PAV/UAV as it related to SCS /SpaceMobile. PAVs (Personalized Aerial Vehicles) are like UAVs but larger with more range,

/2
Apr 1, 2023 • 43 tweets • 21 min read
$ASTS annual report thread.

1/ First a few resources.

Seeking Alpha transcript & voice.

seekingalpha.com/article/459162…
Call link (requires login)

event.choruscall.com/mediaframe/web…

Slide deck: sec.gov/Archives/edgar…

10K sec.gov/ix?doc=/Archiv…

2/
Dec 25, 2022 • 12 tweets • 6 min read
$ASTS satellite #BlueWalker3 in orbit testing is ongoing.

It is the cutting edge of 5g Non-Terrestrial-Network NTN, Direct-To-Handset, DTH, technology.

It has a lot of interesting design choices.

Selected, in tech, standard and regulatory terms as it was purpose built.

1/n Previous schematic of the transparent satellite AST uses is one of two NTN DTH architectures supported by the global 3GPP 5g standard.

The alternative AST opted out of has parts, or all, of the base-station placed onboard the satellite, whereas ASTs is on earth.

2/n
Dec 24, 2022 • 4 tweets • 2 min read
The objective of BlueWalker3 is to test many things. It is a novel form-factor satellite. Q/V backhaul dishes and cellular fronthaul phased array all new.

But if the RF loop is closed on 4g/5g protocols I would call that a success.
If broadband speeds are achieved, even better. Regarding cellphone speeds. It is a common missunderstanding that the experience increases linear with speed.

Beyond 1.5 Mbps the experience improves some, but little.

In interviews Abel Avellan has said he expects 30 Mbps per cell in production satellites.

2/n