Attch 2 - Additional Specs ROM.pdf

Request details for: geostationary transponder bandwidth for an international two-way time/frequency transfer network Jeff A. Sherman (jeff.sherman@nist.gov, +1 303-497-3511) Time realization and distribution group (688.40) Time and frequency division (688) National Institute of Standards and Technology (NIST) 325 Broadway Boulder, CO 80305, USA Last updated: 15 May 2026

Section 1: summary NIST seeks information on availability and cost of geostationary satellite Ku-band transponder bandwidth to support a high-precision time transfer network of national metrological institutes (NMIs) and other laboratories.

Section 2: description of application Currently, up to nineteen NMIs or other laboratories in North America and Europe employ a technique known as two-way satellite time/frequency transfer (TWSTFT) to regularly compare realizations of Coordinated Universal Time (UTC) based on one or several laboratory-operated atomic clocks.

The network currently operates using three transponders on the satellite Telstar 11-N with a service contract ending November 26, 2026. To allow for uninterrupted observations, we seek to establish a new contract for compatible service to begin no later than November 27, 2026.

The TWSTFT technique is similar to code-based satellite ranging and requires so-called “bent pipe” transponder service; i.e., signals from Earth are only translated in carrier frequency and re-amplified on the satellite for Earth-bound retransmission. Specialized modems transmit a pseudorandom noise (PRN) code, where the symbol modulation timing is tightly linked to a local atomic clock or time scale. A remote modem measures the round-trip signal delay (ground station A to satellite to ground station B) by maximizing the correlation between the received signal and a variably delayed synthesis of the PRN code.

Both modems engaged in a link transmit and receive in this manner; by exchanging a few minutes of measurement data the time-difference between laboratory clocks can be determined with a precision of about 100 ps. Measurement precision increases roughly in proportion to the code modulation rate (and therefore, occupied bandwidth). Relatively little data throughput is required.

mailto:jeff.sherman@nist.gov

Section 3: desired specifications Table 1 below lists desired specifications, some of which are necessary for compatibility with existing equipment. Table 2 lists details about participating Earth stations.

Table.7¿.Desired.specifications.for.geostationary.transponder.service

Area of coverage North America, Europe; station locations in Table 2 below Service type Non-preemptable Ku-band transponder bandwidth Satellite type Geostationary, station-kept Uplink range 14.0 GHz to 14.5 GHz Downlink range 10.95 GHz to 12.5 GHz Polarization Linear, uplink/downlink are cross-polarized. No polarization changes to switch between a North America/Europe link and a Europe/Europe link.

For transatlantic links… Single transponder covering all Earth stations (detail subsection 4a below), or several transponders including “cross-strapped” arrangements for North America/Europe and Europe/North America (subsection 4b below).

Satellite longitude Approximately 30°W through 45°W Satellite EIRP ≥ 42 dBW Earth station modem TimeTech SATRE [1] Earth station frequency control

Modem and transmitting up-converter PLL to atomic clock reference frequency.

Earth station antenna sizes, max. powers

See Table 2 below

Network type CDMA Modulation type BPSK Modulation rate 2.5 Mc/s Occupied bandwidth Approximately 3.75 MHz (at -6dB, for 2.5 Mc/s code), subject to carrier’s transmission plan Optional modulation rates/bandwidths

Interested in cost/availability for supporting higher rates: 5.0 Mc/s (approx. 7.5 MHz), 10.0 Mc/s (approx. 15 MHz) , 20.0 MHz (approx. 30 MHz). Price per MHz is useful, if available.

Term One year (November 27, 2026 through November 26, 2027)

Billing Laboratories have agreed to a cost sharing arrangement:

25% billed to NIST, USA 25% billed to USNO, USA 50% billed to PTB, Germany

Table.8¿.Earth.station.locations.and.operating.equipment

# Location ID Antenna size (m)

Nominal Tx power (W)

Max. Tx power (W)

Active stations in North America 1 Boulder, CO, USA NIST 3.7 0.5 1 2 Washington, DC, USA USNO 4.5 1 5

Active stations in Europe 3 Delft, The Netherlands VSL 2.4 1 5 4 Braunschweig, Germany PTB 1.8 6.3 8 5 Torino, Italy IT 1.8 4 4 6 Boras, Sweden SP 1.8 1.5 8 7 Paris, France OP 2.4 0.1 8 8 San Fernando, Spain ROA 1.8 4 4 9 Lisboa, Portugal IPQ 1.8 4 4 10 Teddington, United Kingdom NPL 2.4 0.2 6 11 Bern, Switzerland CH 1.8 0.4 4 12 Borowiec, Poland AOS 2.4 4 8 13 Plateau Calern, France OCA 1.8 4 4 14 Besançon, France LTFB 2.4 0.1 16 15 Fucino, Italy PTF01 1.8 2 8 16 Oberpfaffenhofen, Germany PTF02 1.8 2 8 17 Stuttgart, Germany TIM 1.8 2 8 18 Kocaeli, Turkey UME 1.8 2 8 19 Warsaw, Poland PL 1.8 2 8

Section 4: transatlantic service options Only one of the following service options for implementing the transatlantic links (North America to Europe and Europe to North America communication) will be selected. To give clarity we cite some examples of satellite transponders that may qualify.

Subsection.0a¿.single.transponder The service is met by a single Ku-band transponder, with footprint covering all the Earth stations listed in Table 2. From publicly available information, example transponders include:

Intelsat 32e, 43 °W, transatlantic WBVD beam

For power budgeting in this mode, assume all stations may transmit simultaneously.

Subsection.0b¿.up.to.three.transponders.with.»cross‗strapped‹ .beams The Europe-to-Europe service is made with one transponder. North America to Europe and Europe to North America service is accomplished with a pair of “cross-strapped” transponders/beams. European stations must be able to switch between the Europe/Europe and Europe/North American links with no change in polarization or pointing. From publicly available information, example sets of transponders include:

Telstar 11-N, 37.5 W: USCarribean -> Europe, Europe -> USCarribean, Europe->Europe

SES 6, 40°W: NA -> East Atlantic East Atlantic -> NA East Atlantic -> East Atlantic

Intelsat 35e, 34°W: Caribbean->EuropeMDT EuropeMDT -> Caribbean EuropeMDT -> EuropeMDT

Hispasat 30W-5, 30°W: Americas1E -> Europe1E Europe1E -> Americas1E Europe1E -> Europe1E

For power budgeting in this mode, assume 14 of 17 European stations may transmit simultaneously on the Europe->Europe transponder. At most, two European stations will transmit to two North American stations (and vice versa) simultaneously on the transatlantic “cross strapped” transponders.

Section 5: additional information [1]: TimeTech SATRE modem specification:

https://www.ion.org/ptti/upload/files/1039_10139_Datasheet.pdf