DINO Communication System

DINO PDR April 21, 2023

DINO Communication

System

Zach AllenHosam Ghaith

Mike Li

Colorado Space Grant Consortium


Purpose

• Establish two-way communication link between satellite and ground station.– Link must allow transfer of map files from

satellite to ground.– Must allow transmission of health and status

data from satellite to ground.– Must allow the satellite radios and flight

computer to receive command lines transmitted by ground station.



Requirements Imposed by other Subsystems

• Data Rate: must be high enough to accommodate all data– 20 kbytes per topographical map– 255 bytes per Health and Status Packet– 5 kbytes per uploaded schedule

• Antenna– Non-deployable patch (preferable): constrained to

25.6 cm by 25.6 cm space.– Deployable monopole: must be shorter than 47.5 cm.



Requirements Imposed by COMM on other Subsystems

• Power:– Receiver: 5 V at 90 mA (450 mW)– Transmitter

• Active mode: 12 V at 1.4 A (16.8 W)• Idle mode: 12 V at 90 mA (450 mW)

– External TNC (tentative): 12 V at 400 mA (4.8 W)• Data:

– Map files should not exceed approx. 25 kB in size.



Requirements Imposed by COMM on other Subsystems

• Structures– Mass

• Two Transceivers– 170 grams each– 2 x 170 grams = 340 grams total

• External TNC– 40 g

• Antenna– Patch << 1kg– Monopole: 23 g

– Dimensions• Two Transceivers

– 4.9 x 2.3 x 1.2 inches each• External TNC

– 6.1 x 7.3 x 1.3 inch• Antenna

– Patch 9.8 x 3.9 x 0.07 inch– Monopole: 18 inches long

» 17 inch x 1/8 inch» 1 inch middle section that is 1/2 inch wide



Subsystem Block Diagram

• All Data lines use RS-232 Serial

• Transmitter operates at 12 V when active, 5 V idle.

• Receiver operates at 5 V.• External TNC: 12 V line,

allows 9,600 bps link to ground.

• Internal TNC proven to be reliable at 1,200 bps.

12 V line voltage(5 V when idle)1.4 A16.8 W transmitting(450 mW idle)

5 V line voltage90 mA450 mW(constant)

12 V line voltage400 mA, 4.8 W(constant)

RS-232 Serial9,600 bps(during setup only)

RS-232 Serial9,600 bps(during setup only)

RS-232 Serial9,600 bps(constant)

Transmitter

Kenwood TH-D7

Receiver

Kenwood TH-D7

External Terminal Node Controller(TNC)

InternalTNC

InternalTNC

Antenna

Power LineData Line

Legend



Design

• Transceivers– Two Kenwood TH-D7 radios: dual band 70cm / 2m, with internal TNC’s.– Reasons

• Allows two distinct channels for uplink and downlink, respectively.• Built-in TNC.• Heritage from 3CS mission.

– 70 cm downlink, 2m uplink.• TNC – Two options:

– External TNC: Timewave PK-96• Advantage: performs well at 9,600 baud.• Disadvantages:

– Requires modifying the Kenwoods’ filters to achieve 9,600 baud.– Requires additional mass, volume, and power.

– Internal TNC• Advantage: proven to perform reliably at 1,200 baud on previous missions.• Disadvantage: Greatly reduces data rate.



Design (continued)

• Antenna– Patch

• Pros– Preferable gain pattern– Non-deployable

• Cons– Could occupy a lot of space on nadir surface– Complicated design process– Expensive

– Monopole• Pros

– Simple design– Does not take up space on the satellite’s surface

• Cons– Deployable



Illustration of Patch Design

Metal Patch

Dielectric Substrate

r = 37 ± 1

~25 cm

~10 cm

145 MHz coax feed436 MHz coax feed

Mount on Nadir Plate



Illustration of Monopole Design

Dual Band Monopole Deploy from Nadir Plate



Analysis: Power Requirements

• Daytime Operation– Receiver: 0.45 W (5 V, 90 mA) always.– TNC: 4.8 W (12 V, 400 mA) always.– Transmitter: 16.8 W (12 V, 1.4 A) for approx. 2 minutes,

otherwise same as Receiver (0.45 W).

• Nighttime Operation– Receiver: 0.45 W (5 V, 90 mA) always.– TNC: 4.8 W (12 V, 400 mA) always.– Transmitter: 16.8 W (12 V, 1.4 A) for approx. 4 seconds,

otherwise same as Receiver (0.45 W).

• Safe Mode– Same as nighttime.



Analysis: Calculating Transmission Time

• We need to find the transmission time in order to find the exact power requirements over the course of one day.

• Time needed to send one packet:– 10 bits/byte * 256 bytes/packet 1200 bits/sec =

2.133 sec/packet• Total transmission time (assuming 25 kB per pass during

daytime):– 2.133 sec/packet * 25 kB/pass

256 bytes/packet = 208.3 sec/pass = ~ 3.5 minutes (absolute minimum)

– May be approx. twice the minimum (resending, errors, etc.)

– This is a realizable amount of time.



Analysis: Link BudgetElement Parameter Value Units

Transmitter (Tx)1 Tx Power, Pt 37.0 dBm2 Tx Component Line Losses, Ltl 0.5 dB 3 Tx Antenna Gain (Peak), Gt 2.0 dBi4 Tx Pointing Loss, Ltp 0.0 dB5 Tx Radome Loss, Ltr 0.0 dB

6 EIRP (1-2+3-4-5) 38.5 dBm

PropagationTransmission Frequency, f 436.0 MHzSlant Angle 5.0 degOrbital Altitude, h 425.0 kmLink Range, R 12660.6 kmPropagation Factor, n 1.0

7 Free Space Loss, Ls 167.3 dB8 Atmospheric Absorption, Lpa 0.5 dB9 Precipitation Absorption, Lpp 0.5 dB

10 Total Propagation Loss (7+8+9) 168.3 dB

Receiver (Rx)11 Rx Antenna Gain (Peak), Gr 15.0 dB12 Rx Polarization Loss, Lrpol 3.0 dB13 Rx Pointing Loss, Lrp 0.0 dB14 Rx Radome Loss, Lrr 0.0 dB15 Rx Component Line Losses, Lrl 0.5 dB16 Rx Implementation Losses, Lri 1.0 dB

17 Received effective carrier power -110.8 dBm(6-10+11-12-13-14-15-16)

Noise18 Standard Thermal Noise, kT -174.0 dBm/Hz19 Rx Noise Bandwidth, B 43.0 dBHz20 Rx Noise Figure, NF 10.0 dB

21 Effective Noise Power (18+19+20) -121.0 dBm

Results22 Available CNR (17-21) 10.2 dB23 Data Rate 39.8 dBHz24 Available Eb/No (22+19-23) 13.4 dB25 Implementation Losses 2.0 dB26 Required Eb/No 13.0 dB27 Margin (24-25-26) 6.4 dB

Link Budget Form courtesy of Dr. Stephen Horan, New Mexico State University.



Link Budget (cont.)

• Margins for different slant angles– 5 deg: 6.4 dB– 12.5 deg: 9.1 dB– 15 deg: 10.1 dB

Diagram Reference:Vincent L. Pisacane and Robert C.

Moore, Eds., Fundamentals of Space Systems. New York: Oxford University Press, 1994.



Test Plan

• Set up ground station in flight configuration• Setup spacecraft in flight configuration (deploy

antennas if necessary)• Transfer files to and from spacecraft CDH

system• Measure throughput• Adjust link as necessary



Parts List and Estimated Costs

• Transceivers– Two Kenwood TH-D7 radios: one for uplink, the other

for downlink.– Uplink: 2 m band (~145 MHz), Downlink: 70 cm band

(~436 MHz).– Cost: $359.95 each.

• External TNC (tentative)– Timewave PK-96

• Cost: $219.95



Parts List (continued)

• Patch antenna parts– Dielectric Substrate as big as 10 x 10 inches

• Need at least two: one for testing, other for flight• Cost: anywhere between $20 and $200

– Metal Patch– Coaxial Feed

• Monopole Antenna– Cost: $30 (Estimated)



Issues and Concerns

• Patch Antenna Issues– Design process still in early stages: no absolute guarantee that

the patch will work within the allocated space.– High dielectric substrate may prove costly (+$200).– May not be able to achieve correct polarization: 3 dB loss in

power.• Monopole Antenna Issues

– Impedance matching complicated for dual band tuning – may need two antennas.

• Baud Rate Issues– Must learn how to connect external TNC to radios to achieve

9600 bps baud rate.– Internal TNC’s not known to perform well at other than 1200 bps

(which may be too slow), but proven reliable at 1200 bps.

Documents

DINO Communication System