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66 -- TIME SCALE MEASUREMENT SYSTEM SOL 52RANB00C020 DUE 052600 POC Procurement Technicians, 303/497-3221, FAX 303/497-3163 E-MAIL: NOAA; MASC Acquisition Management, masc.solicitation@noaa.gov. The National Institute of Standards and Technology (NIST) requires the upgrade of the system that measures the time differences of the atomic clocks in the NIST times scale. The measurement system is at the heart of UTC(NIST) and requires sub picosecond stability and a very high degree of reliability. Two independent and identical systems will be procured. The two new systems shall have channels that accept sinusoidal input signals from hydrogen masers or high stability cesium beam atomic frequency standards at 5 and 100 MHz (10 MHz optional). To provide improved accuracy and stability of the measurement system, a low noise frequency synthesizer, which is referenced to one of the atomic frequency standards, shall generate a reference output signal that is coherently offset by a nominal 10 Hz. The nominal 10 Hz beat frequencies between the output of the reference synthesizers and the 5 or 100 MHz outputs of each of a number of other atomic frequency standards are the signals that are actually measured. The input impedance of the RF channels shall be 50 ohms with a maximum return loss of 30 dB at 5MHz and 20 dB at 100MHz. All RF inputs shall have DC isolated grounds and the connectors shall be SMA. A minimum of 24 input channels in each system shall be required. There shall be a minimum of 8 channels for 100 MHz and 16 channels for 5 MHz. At the option of the Government, additional channels for 10 MHz may be added or replace some of the 5 MHz channels. Ultimately 192 channels may be required. The design shall be modular in nature so that more measurement channels can be added at a later time. Designs based on measurements at 1 pulse per second cannot satisfy the requirements, and all such designs are unacceptable. The information outputted from each measurement channel shall be: (1) the number of cycles of the nominal 10 Hz beat frequency. (2) The phase difference between the nominal 10 Hz beat from the reference oscillator and the test oscillators. (3) Error and status information as described in the full set of specifications. At least 24 channels shall fit in a standard 19-inch rack with a maximum height of 34 cm (14 inches) and a maximum depth of 53 cm (21 inches). The unit shall run off of 120 VAC, single phase in a normal room temperature environment. The computer interface shall be standard computer hardware and shall use an industry-standard interface design such as the PCI bus or the VME bus. Designs based on the (E)ISA standards are not acceptable, since these interfaces are becoming obsolete now and are unlikely to be widely supported in a few years. The controlling computer and its operating system will be supplied by NIST, and will be chosen based on the detailed interface design proposed by the contractor. NIST will consider a design based on any generally-available operating system that is currently supported by its supplier. The maximum acceptable instability for a time difference measurement on the 100 MHz channels is 0.06 ps TDEV at 1 s for a measurement rate of once per second. The corresponding maximum Allan deviation at 1s is 1e-13. For longer time intervals, tau, the Allan deviation shall decrease as 1/tau to 1e-16 at 1000 s. At 100,000 seconds it shall not exceed 1e-17. Beyond tau equals 1e6 s the Allan deviation shall not exceed 1e-18. Better performance is highly desirable and a goal for the 100 MHz signal is an Allan deviation at 1 s of 1e-14. The stability goal should be such that the Allan deviation decreases as 1/tau, or faster, to a level of 1e-19 and never exceeds that value. The Allan deviation of the measurement systems shall be determined by using two independent systems to measure the same clock, and it shall be assumed that the two systems are equivalent. Similar tests shall also be performed with two channels on the same system. Delivery of the two systems shall be 240 calendar days after Contractor's receipt of a notice of award. Delivery shall be F.O.B. Destination to NIST, 325 Broadway, Boulder, Colorado 80303-3328. Standard Industrial Classification code is 3825. Small business size standard is 500 employees. See Numbered Note 1. Posted 04/12/00 (D-SN444122). (0103)

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