1. 5 Section 11.0 Communications Subsystem Space Technology
GSFC 5
Space Technology
“Tomorrow’s Technology Today”
Section 11.0
Communications Subsystem
Victor J. Sank
Communications Lead Engineer
ST5 PDR June 19-20, 2001

2. Agenda Key Requirements Documentation Allocations
Transponder, Diplexer and HPA Layout
System Concept Design
Link Budgets
Antenna
Block Diagram
Development
Testing
Issues
Back-up Slides

3. System Requirements
S/C shall implement X-band communications link with the ground. (MRD )
The spacecraft shall be able to downlink telemetry and receive uplinked commands. (MRD )
The transponder system shall be capable of decoding “special/hardware" commands from the uplink without the use of the CDH or FSW and execute discrete pulse signals to other units on the spacecraft. (MRD )
The spacecraft shall have two, ground selectable, downlink data rates; 1Kbps and 100Kbps. (MRD )
The spacecraft shall be able to support 2-way radiometric Doppler tracking. The system radiometric Doppler tracking accuracy shall be sufficient to support ground antenna pointing at distances of 2 to 5 Re. (MRD and MRD )
The spacecraft shall provide a minimum RF output power of 1.5 W, measured at the antenna port of the diplexer. (MRD )

4. Derived Requirements
10MB HK and Science data playback plus RT HK in min contact
11m Ground Antenna (minimum)
Convolutional coding on telemetry , r = 1/2, K = 7
Due to the use of 1/2 rate convolutional encoding, the necessary symbol rate (in kilosymbols per second, Ksps) is twice the required data rate (in kilobits per second, Kbps).
Coherent RF turn around using CCSDS recommended ratio
Stable oscillator

5. Documentation

6. System Allocations Mass Volume DC Power Thermal Operate Survive
Transponder Unit Kg
Front End Unit (Dplxr & HPA) Kg
Antenna Kg
System Total Kg
Volume
Transponder Unit cm3
Front End Unit cm3
Antenna cm3
DC Power
Rcvr Only W
Rcvr and Xmtr W
Thermal Operate Survive
Transponder, HPA & Dplxr to 50 °C to 60 °C
Antenna to 40 °C to 80 °C

7. Transponder, Diplexer and HPA Layout
(2.95 x 2.45 x 1.97 in)
Diplexer
(3.3 x 1.1 x 0.5 in)
HPA
(3.0 x 1.5 x 0.6 in)
Scale: 3”

8. Communications System Design Concept (1 of 2)
Performance
Two Data rates baselined; 1 and 100 Kbps
At <5Re Data transfer of 100Kbps with a BER of <1X10-5
Two-way, Coherent Doppler Tracking is baseline
One-way Doppler will provide backup orbit determination
Other Attributes
5V transponder, excluding HPA
HPA mount point minimizes thermal variation at Oscillator
X-band Uplink and Downlink
3 dB margin in Telemetry link budget
>20 dB in Command link budget

9. Communications System Design Concept (2 of 2)
Frequency and Spacecraft ID Registration (MRD )
NTIA Frequency allocation approval; currently Stage 2
X-band MHz downlink, MHz uplink
S-band MHz, MHz
CCSDS GSCIDs assigned; minimum Hamming distance 4;
(used to uniquely identify spacecraft in CCSDS frame header)
ST E0
ST E
ST B
SOMO/CSOC SCIDs assigned (for ground handling of data) ST ST ST

10. Link Budget: X-band Space – Ground (1 of 2)
1 Transmitter Power (W) dB
2 Antenna gain (dB)
3 SC Antenna beamwidth (°) FWHM
4 Passive Loss (dB) cables, etc.
5 EIRP (dBW) dBm
6 Freq. (MHz)
7 Range (km) Re
8 Space loss (dB)
9 Atmos, Scint, Rain Att (dB) high elevation
10 Polarization loss (dB)
11 Rcvd power den (dBW/m2)
12 Rcvd PSD over 4 KHz convo coded

11. Link Budget: X-band Space – Ground (2 of 2)
13 Ground antenna size (m) ft
14 Antenna gain (-surf loss)(dB) % eff
15 Antenna beamwidth (deg) FWHM
16 Power Received (dBm) Bkg Temp 40K
17 Antenna to LNA Loss (dB) diplexer Temp 75.09
18 LNA gain (dB) N=1.2dB, T=92.29K
19 System temp (deg K) dB K
20 System G/T (dB/K) L14 - L19
21 C/No (dB-Hz) L12 + L
22 Data rate (bps) dB (N = dBw)
23 Implementation loss (dB) Rcvr and BS
24 Avail Eb/No (dB) L21 - L23 - L24
25 Eb/No required (dB) E-5 coded (4.2 ideal)
26 Avail margin (dB) Line 24 - Line 25

12. Link Budget: X-band Ground – Space (1 of 2)
1 Transmitter Power (W) dB
2 Antenna gain (dB) m
3 SC Antenna beamwidth (°) FWHM
4 Passive Loss (dB) cables, etc.
5 EIRP (dBW) dBm
6 Freq. (MHz)
7 Range (km) Re
8 Space loss (dB)
9 Atmos, Scint, Rain Att (dB)
10 Polarization loss (dB)
11 Rcvd power den (dBW/m2)
12 Rcvd PSD over 4 KHz

13. Link Budget: X-band Ground – Space (2 of 2)
13 Space antenna size (m) omni
14 Antenna gain (-surf loss)
15 Antenna beamwidth (deg) FWHM
16 Power Received (dBm) Bkg Temp 40K
17 Antenna to LNA Loss (dB) diplexer Temp 75.09
18 LNA gain (dB) N=3 dB, T=288.63K
19 System temp (deg K) Bkg 40. dB K
20 System G/T (dB/K) L14 - L19
21 C/No (dB-Hz) L12 + L
22 Data rate (bps) dB (N = dBW)
23 Implementation loss (dB) incl mod & diff coding
24 Avail Eb/No (dB) L21 - L23 - L24
25 Eb/No required (dB) E-5 uncoded
26 Avail margin (dB) Line 24 - Line 25

14. ST5 Quadrafilar Helical Antenna
Beamwidth to +60º from ecliptic
Receive Gain 0dB
Transmit Gain 0dB
Operating Frequency: 8.47 GHz
LHCP
Diameter: inches
Length: inches
Turns: 1
Trace: copper
Dielectric core: EccoStock LoK
(Dielectric Constant =1.7)
Notes:There are four traces in the dielectric core.
Traces are 90° apart from each other.
Traces do not touch each other.
Drawing not to scale.

15. Antenna Gain (Stand alone)
-180
-160
-140
-120
-100
-80
-60
-40
-20 20 40 60 80
100
120
140
160
180
Antenna Gain (Stand alone)
ST5 Quadrifilial Helical Antenna 5 -5
-10
(Gain in dB)
-15
-20
-25
-30
Angle (Deg)
LHCP
RHCP

16. Antenna Gain with Choke Rings
-50
-40
-30
-20
-10 10
-180
-155
-130
-105
-80
-55 -5 20 45 70 95
120
145
170
Degree
Gain (dB)
LHCP
RHCP
ST5 Ideal Antenna with Choke Ring

17. Transponder Functional Block Diagram
Auxiliary Command Inputs
UpLink Lock to C&DH Cmd Decoder
Special Command Detector
C&DH Data
C&DH Clock
LNA
Command
Receiver
Special
Cmd reset
Coherent Reference Rx
Status
Rx/Tx Status Output to C&DH
Status/Control
Transponder Controller
X-band Up/Down
Diplexer
Control
Transponder Mode Control from C&DH Tx
LO Generator
Oscillator
Downlink Clock to C&DH
HPA
Transmitter
Telemetry
Downlink Telemetry from C&DH
Front End Units
Transponder
+7.2Vdc
+5Vdc

18. Transponder RF Block Diagram
113
244
636
Loop
Filter
9.625 MHz
TCVCXO
DIPLEXER
SPLITTER
DRV
LNA
VGA
BPF
LPF
MODULATOR
VECTOR
ZERO-IF
RECEIVER
BASEBAND PROCESSOR
MHz
MHz
MHz
MHz
MHz
AGC
RX I
RX Q
TX Q
TX I
FROM BASEBAND
PROCESSOR
Front-End
Assembly
TRANSMITTER
C-BAND SYNTHESIZER
DUAL
SYNTHESIZER
CONDITIONING RX
TRACKING
REFERENCE
TUNING TX
C&DH
INTERFACE
SPECIAL
COMMAND
DECODE
TX DATA
RX DATA
LOCK DETECT
ADC
HPA
Electronics Unit
C& DH

19. L, C and S-band Synthesizers

20. Transponder Digital Block Diagram
Tracking RX
Conditioning
Data Clock
Generation
Special
Command
Decode
C&DH
Command /
Status
Interface
LPF,
2kHz-
1MHz
I from
Tuner IC
Q from
I in
Q in
RX Data
Data out
9.625
MHz
VCO
To Synth.
Master
Clock
Lock Indication
& other status
Oscillator
Control
Q out
I out
RX Clock
TX Clock
Commands
/ Status
Parameter change / status read
ADC
Clocking TX
Data Out
Data In
Synthesizer setup &
other commands
Radio
status
interface
Discrete
Hard & Soft
C&DH Reset
C&DH Cmd
& Status
Out
TX Data
6-8 bit
DAC or
Resistor
Ladder
To Modulator IC
To AGC
AGC +/-
Loopback
(2 rates, and
set-to-nominal)
8 bit
XpdrReset
Soft Reset
Bit Lock
Carrier
Detect
Signal Detect ó õ

21. Communications System Development
Transponder System Development
Transponder being designed under phase 2/3 SBIR
Will result in breadboard/test unit and Qual unit
Firm fixed price (FFP) contract expected for flight units
After Transponder CDR, Aug 2001, contract for flight units will be issued
No Heritage; New technology, 5 volt, digital, single reference oscillator
New development. Requires full qualification
Antenna Development
In progress at GSFC Code 567
Feed blanks under contract with Emerson & Cuming
Polyflon to lay traces on blank feeds
Have prototype Choke Ring Assembly; needs final design and fab

22. Communications System Technology
Technology Characteristics
Receiver and transmitter will use common frequency synthesis (common to any transponder)
Under development by AeroAstro
Technical Readiness Level is currently about 3/4
Untested conventional design, Hardware prototyping

23. Testing and RFGSE
Test Program is under Development per ST , Component Test Requirements and Guide Lines
Will include compatibility and performance characterization
RFGSE
One RF Rack to include
PSK Modulator/Xmtr (µdyne TSS-2000)
S-band Receiver (µdyne MRB-1200 or 700)
Upconverter (Miteq UP-25020)
Downconverter (Miteq DN-25020)
Spectrum Analyzer (HP 8596E)
Oscilloscope (HP54602B)
Plotter/Printer/PC
Power Meter (HP4418A)
Power Meter Heads (HP8481A, H)
Bit Error Rate Test Set (FBD-6000A or BitAlyzer 26, 400, 622)

24. Risk Mitigation (1 of 2) Risk
Oscillator; 40 weeks ARO for flight units
HPA 1.5 W DC to RF efficiency not confirmed
Diplexer transmit filter may have high insertion loss
DSNBand stop filter may be required that adds to insertion loss

25. Risk and Mitigation (2 of 2)
GSFC is working with AeroAstro to specify and buy the transponder oscillator. GSFC will provide for screening and qualification of the oscillator for flight with the chosen vendor and deliver it to AeroAstro for integration and qualification of the transponder. To mitigate scheduling risk, AeroAstro is building a non flight oscillator for the EM unit. The Qualification Transponder Unit will be fully tested and flight qualified, enabling it to be utilized for flight.
A backup/replacement amplifier has been built by AeroAstro. Its 1.5 W output does not meet the 2.0 W HPA output requirement, but it can be utilized by ST-5, lowering the risk from mission critical to a performance (data rate) issue.
Use of a low insertion loss Diplexer may require an additional band stop/ band reject filter (BRF). The filter needs to have steep cut-off characteristics at the band edges and high selectivity or Q factor and low insertion loss in-band. Even though BRF may not be needed, specifications are being drawn up and filter will be ordered.

26. 5 Back-up Slides Communications Subsystem Space Technology
GSFC 5
Space Technology
“Tomorrow’s Technology Today”
Back-up Slides
Communications Subsystem
ST5 PDR June 19-20, 2001

27. ST5 Mission Overview S/C - Mission Configuration
Satellite constellation technology mission (3 satellites)
GTO orbit, Spin stabilized
< 25 Kg, < 25 watts
X-band space to ground; S-band space to space
Magnetometer
Space - Ground Communication
AeroAstro transponder is 1 of 8 technologies to be demonstrated
Orbit determination via 2 way coherent Doppler
S/C Position Accuracy for pointing 11 m antenna: 10 Km
1 Kbps to 100 Kbps downlink rate, CCSDS format
1 Kbps to 8 Kbps uplink rate, BPSK on X-band carrier

28. Transponder Tracking Block Diagram

29. SINDA/G Thermal Analysis61 45
Oscillator 72 57
Up/Down converter 84 69
Synthesizer 60
Baseband
Max Board Temp(°C)
Max board Temp (°C)
Radio Board
S/C 40 °C
S/C 25 °C

30. CCNT Link Budget: S-band Space - Space
1 Transmitter Power (W) dB
2 Antenna gain (dB)
3 SC Antenna beamwidth (deg) omni FWHM
4 Passive Loss (dB) cables, etc.
5 EIRP (dBW) dBm
6 Freq. (MHz) 2265
7 Range (km) 1000
8 Space loss (dB)
9 Atmos, Scint, Rain Att (dB)
10 Polarization loss (dB)
11 Rcvd power den (dBW/m2)
12 Rcvd PSD over 4 KHz convo coded

31. CCNT Link Budget: S-band Space - Space
14 Antenna gain (-surf loss)(dB) % eff
15 Antenna beamwidth (deg) omni FWHM
16 Power Received (dBm) Bkg Temp 40K
17 Antenna to LNA Loss diplexer Temp 75.09
18 LNA gain (dB) N=3.5dB T=359.23K
19 System temp (deg K) dB K
20 System G/T (dB/K) L14 - L19
21 C/No (dB-Hz) L12 + L
22 Data rate (bps) dB (N = dBw)
23 Implementation loss (dB) incl mod & diff coding
24 Avail Eb/No (dB) L21 - L23 - L24
25 Eb/No required (dB) E-5 coded (4.2 ideal soft)
26 Avail margin (dB) L25 - L26

32. Transponder PDR Review Actions
SCR Held May 10-11, 2000
8 actions assigned, all closed with originator
Transponder PDR October 19, 2000, PDR January 31, 2001
56 RFAs written, 39 closed, 17 Open until Transponder CDR
2 Compliance matrix AA Close, fill by CDR
3 Incomplete items AA Open, close by CDR
10 Present signal characteristic to electrical systems ST5 Done, close by CDR
11 Mechanical, thermal, electrical interfaces AA Done, close by CDR
13 Define resets ST5/AA Done, close by CDR
16 Work with electrical systems on C&DH interface AA/ST5 Done, close by CDR
17 Provide parts list AA Done, close by CDR
29 Parts qualification and testing AA Open, close by CDR
31 Plan for reduced magnetic signature AA Open, close by CDR
35 Specify transponder-C&DH command and telemetry AA Done, close by CDR
above plus special commands ST5/AA Done, close by CDR
46 Phase noise vs tracking accuracy ST5/AA Open, close by CDR
47 Specify limit on spurs to meet system requirements AA Open, close by CDR
49 Show that Cmd format is supported by ground stationsST5 Open, close by CDR
50 Define testing for development and compatibility AA/ST5 Open, close by CDR
53 Develop plans for false and self lock testing AA Open, close by CDR
54 Generate plans for packaging AA Open, close by CDR