ISAS/JAXA Tracking station
Usuda Deep Space Center
• Diameter 10m– AE 44% expected
• Feed & Receiver – Ka-band
• Trx < 50K expected– cooled LNA– Tsys 140 K (fine condition)
Feed DIP
TX-AMP
U/C
D/CLNA
H-Maser
DDS
O/E E/O
E/O O/E
LO O/E E/O
U/C
DDS
LO
D/C
LO
DEM PD
FMT
CLK GEN
LO
LO
Mark5B
Cooled
VSOP-2 Ground System (Based on halca method)
PC
OBSSimulator
CMD/MON Freq, PhaseController
40.0GHz
37.5GHz
100MHz(±2MHz)
100MHz
1100MHz
100MHz(±2MHz)
500MHz
5,900MHz
7,000MHz
26,000MHz
4,500MHz
7,000MHz
7,000MHz 7,000MHz
6,500MHz
100MHz
100MHz
500MHz
100MHz 10MHz
VSI-H
1PPS
1PPS
100MHz
400MHz
400MHz
Freq, PhaseControl
26,000MHz
Software Spectro-scope
Ether
Freq, PhaseControl
Network
Ether
7,000MHz
Ether GP-IB
Antenna Room Operation Center
U/C1,000MHz
LO
FIFO
Carriertrack
Feed DIP
TX-AMP
U/C
D/CLNA
H-Maser
O/E E/O
E/O O/E
LO O/E E/O
LO
D/C DEM PD
FMT
LO
LO
Mark5B
Cooled
VSOP-2 Ground System (w/o Doppler Comp.)
PC
OBSSimulator
CMD/MON Freq, PhaseController
40.0GHz
37.5GHz
100MHz
500MHz
7,000MHz
26,000MHz
4,500MHz
7,000MHz
7,000MHz
7,000MHz
6,500MHz
100MHz
100MHz
500MHz
100MHz 10MHz
VSI-H
1PPS
1PPS
26,000MHz
Software Spectro-scope
Ether
Network
Ether
7,000MHz
Ether GP-IB
Antenna Room Operation Center
LO
FIFO
Doppler compensation needed?
• Related Matters– Band mismatch– PLL Loop stress– Phase characteristics of onboard instruments– Correlator capability– System construction cost
Band mismatch
• Doppler shift: ~1MHz (f=40GHz, rr=7km/s)
• Band-mismatch: 126 MHz (128 – 2 MHz)
• Degradation of SNR : 0.99 (√126/ 128)
PLL Loop stress• Relation between Doppler rate and PLL
thresholderr
Ln
thresholderrn
err
B
,
,2
)2(
: Natural angular frequency of second order loop(rad/sec)
: Rate of change of angular frequency (rad/sec2)
: Phase error of Phase Lock Loop, threshold ( ~12deg.)
HzBL 100
Phase characteristics of instruments
• Phase fluctuation dφ by df :
• Easy estimation – Hup(f)- Hdown(f)=2πfτ– Group delay characteristicsτ: ~ 1nsec– Phase fluctuation dφ ~ 0.36 deg (df~1MHz)
• Phase characteristics measurements needed before launch
2
df)(fHdf)(fH - df)H(f d downdownupup
up
Data Storage• Storage Terminal with VSI
– Mark5B (Haystack)– K5-VSI (NiCT)– Clock fluctuation compensated by FIFO?
• Corrlator interface– VLBA correlator Mark5– ENV correlator Mark5– EAVN* correlatorMark5, K5, VERA terminal*EAVN (East Asia VLBI Network)
East Asia VLBI Network Correlator
• Korea-Japan Joint VLBI Correlator (KJJVC)– KVN and NAOJ
• KVN, VERA, JVN, VSOP-2• Seoul• 16 stations• Data buffer• Data rate
– Max. 8 Gbps/st
Summary
• UDSC 10m antenna is expected to VSOP-2 GTS
• Doppler compensation system depends on cost.
• Several VSI storages are available – Mark5B is better
• for operational easiness at three correlators.