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Spectratime Rubidium Atomic Frequency Standard (RAFS)

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Spectratime RAFS is designed with the latest technologies, providing advanced features, such as long lifetime, high reliability, lightweight and ultra low phase noise, for next-generation space applications.

Applications:

  • GNSS/GPS navigational systems
  • SAR systems
  • FGU systems
  • MRO systems

Key Features:

  • Output 10 MHz and 10 MHz auxiliary
  • Accuracy < 2E-10 after launch & commissioning < 1E-10 under vacuum at delivery
  • Temp -5 to 10C
  • Aging < 1E-10/yr
  • Size (WxHxL) 217x124x117mm | 8.54x4.88x4.6"
  • Weight 3.4 Kg | 7.49 lbs
  • Lifetime/MTBF > 15 yrs / < 2000 fit span>
  • Power (operating) < 35W
  • Voltage 28V
  • Warmup <60W

DESCRIPTION

The Rubidium Atomic Frequency Standard (RAFS) is a state-of-the-art ultra-stable  atomic clock able to deliver a frequency  stability  of about 2x10-14 over averaging intervals of 10’000 s.

The RAFS unit is composed of two main parts. The clock it-self named “RAFS core” and the Electronic  Power Conditioning name “EPC”

which includes the DC/DC converter  and the electrical interface to the satellite. The EPC design could be adapted to the satellite need.

The RAFS is a Rb clock. The Rb clock essentially consists of a voltage-controlled crystal oscillator (VCXO) which is locked to a highly stable atomic transition in the ground state of the Rb87 isotope. While the frequency  of the VCXO is at the convenient  standard frequency  of

10 MHz, the Rb clock frequency is at 6.834  GHz in the microwave  range. The link between  the two frequencies is done through  a phase- stabilized frequency multiplication scheme whereby a synthesized frequency is admixed to enable exact matching.

SPECIFICATIONS

Parameter

value

Unit

PERFORMANCES

Frequency (sine)

Main

Auxiliary

10.00

10.00

MHz

MHz

Frequency accuracy

after launch & commissioning phase : Under vacuum conditions at delivery

≤  2 x 10-10

≤  1 x 10-10

 

Freq. Stab Short Term (max / Typical)

1 sec

10 sec

100 sec

1000 sec

10000 sec (drift removed)

flicker floor (drift removed)

Max:

5 x 10-12

1.3 x 10-12    

5 x 10-13 

1.8 x 10-13 

5 x 10-14 

5 x 10-14 

Typical:

3 x 10-12

1 x 10-12

3 x 10-13

6 x 10-14

3 x 10-14

2 x 10-14

 

Freq. Stab Long Term (typical)

< 1 x 10-10

Per year

Outputs Signal Level

13 ±1

dBm

Return loss power ON conditions

(nominal output impedance 50 Ω)

> 20

dB

Spurious Signals (band +/- 2MHz) Outside

< -80

< -60

dB

dB

Harmonics

< -40

dBc

Phase Noise (TBD MHz)

1Hz

10 Hz

100 Hz

1000 Hz

10000 Hz

100000 Hz

-90

-120

-130

-140

-145

-145

dBc

dBc

dBc

dBc

dBc

dBc

PHYSICAL CHARACTERISTICS

Envelope and dimensions

L=217

W=124

H=117

mm

mm

mm

Mass

max. 3.4

Kg

Stiffness

> 100

Hz

OPERATIONAL REQUIREMENTS

   

Design Lifetime

> 15

Years

INTERFACES

ELECTRICAL POWER INTERFACE

Normal Power Line Voltage

28 V nominal Or

50 V nominal

 

TM/TC INTERFACE

TC List

RAFS ON

RAFS OFF

HLC

HLC

 

TM List

RAFS ON/OFF (isolated)

RAFS Lock Indication

RAFS Rb Light

RAFS Rb Signa

RAFS VCXO control

I/P Main Bus Voltage

Main Bus Current

TCB Temperature

EPC Temperature

Relay/Switch

Digital 0 or 5

0-5

0-5

0-5

0-5

0-5

NTC

NTC

V

V

V

V

V

Additional Info

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