Annex B: HEO Satellite Mission

Transcription

1 Annex B: HEO Satellite Mission

2 Table of Content TABLE OF CONTENT...I 1. INTRODUCTION General Response Guidelines BRAODBAND CAPACITY Mission Overview HEO constellation Alternatives Payload Platform Operating Frequencies Satellite Antenna Beams Polarisation Payload Performance Frequency Plans Connectivity Plans Uplink Channels to Beam Connectivity Plan Downlink Transponders to Beam Connectivity Plan Redundancy and Reliability Transponder Charectersitics Non-linearity FGM and ALC Modes Passive Intermodulation Overload Protection Operational Lifetime and Power Budgets Ground Control Segment TACTICAL CAPACITY (UHF) OPTIONAL BROADBAND CAPACITY EXTENSION (X-BAND)...9 i

3 1. Introduction 1.1. General The (NDLO) is currently in the process of planning for satellite capacity intended for governmental use. One of the solutions under consideration is to acquire a space segment implemented by means of a High Elliptical Orbit (HEO) satellite constellation. In this process it is of importance for NDLO to gather information concerning the technical solutions as well as budgetary price information. This document outlines a technical definition of this concept. It defines a Broadband Capacity as described in Section 2, a Tactical Capacity (UHF) as described in Section 3, and an Optional Broadband Capacity Extension as described in Section 4. Also, specific questions (in Bold Italic) are stated in different sections. The industry is invited to comment on and discuss this technical definition, and to provide answers to the specific questions. Budgetary prices including delivery time, should comprise Launch of a HEO satellite constellation, including a re-launch, if the first launch is a failure. The necessary ground control system. Note: Figures in square brackets throughout the document are approximate and to be defined Response Guidelines The response to this RFI should be provided according to the following guidelines: 1. The technical description of the mission shall be divided as follows: i. Broadband Capacity alone. ii. Broadband Capacity + Tactical Capacity. iii. Broadband Capacity + Tactical Capacity + Optional Broadband capacity Extension 2. Payload block diagrams (at system level) and platform configuration shall be presented in all those three cases. The descriptions should be brief and concise, and should be provided in a separate document. If other technical solutions than define in this document will give a more cost effective satellite, the manufacturer is invited to present these. The country of origin for manufacturing of payload and bus, and also name of launcher and launch site, shall be provided. 3. Answers to specific questions in bold italic shall be given in a dedicated document 4. The complete budgetary price scheme shall be given for the Broadband Capacity, while the cost impact associated with adding the Tactical Capacity and the optional Broadband Capacity Extension shall be given as delta costs. The price information should be provided in a separate document. 1

4 2. Braodband Capacity 2.1. Mission Overview HEO constellation Alternatives Currently there is no decision regarding the satellite constellation and different options are being investigated. There may be two possible alternatives: 1. The first alternative is to acquire two satellites that are put in 16 hours critical inclined orbits. 2. The second alternative is to acquire two satellites in critical inclined orbits (Molnyia orbits). Later on, a third satellite could be added to this constellation increasing the communication capabilities. Q1. One of the main concerns is the minimum elevation angle seen from the coverage area. Please comment on this with respect to different constellations. Table 1 summarises the 2-3 suggested alternatives given above. For each of the alternatives the budgetary price shall be given for the baseline constellation. For the additional satellite in Alternative 2, the budgetary price shall be given separately. Table 1: HEO constellation alternatives. Orbit period time Baseline constellation Budgetary price Additional satellites Alternative 1 16 hours 2 satellites Alternative 2 12 hours 2 satellites 1 satellite Budgetary price Payload The broadband communication subsystem is going to have four (4) X-band transponders, and two (2) partially overlapping spot beams. It shall be possible to operate any communications channel independently in both Fixed Gain Mode (FGM) and Automatic Level Control (ALC) mode. The required mode will be selectable by ground command for each channel Platform The requirements for the satellite platform are motivated by: 1. CONVENTIONAL DESIGN, with successful heritage of previously developed systems and units, verified, and based on flight-proven technology. 2. MAXIMUM RELIABILITY, using redundant equipment in every critical point or activity identified in the design. 3. ROBUST, SIMPLE and EASY to OPERATE system design. 2

5 2.2. Operating Frequencies The operating frequencies for the capacity are defined as follows (X-band): Uplink: GHz Downlink: GHz RHCP shall be used for uplink and LHCP shall be used for the downlink Satellite Antenna Beams The X-band capacity shall have 2 partially overlapping circular antenna beams, with coverage areas as shown in Figure 1. The reception and transmit beams shall be coverage areas defined as circular zones concentric about the same bore sight. The cone-angle of the antenna coverage, as seen from the satellite, is also given in Figure 1. The directivity is calculated using an antenna efficiency of Q2. Please elaborate how this coverage area can be realized PBX2 PBX1 Spot Beams PBX1 and PBX2 Cone angle Directivity, EoC 3 [34 dbi] Figure 1: X-band coverage plot Polarisation All communication antennas on the satellite shall be circularly polarised, and be specified with state-of-the art polarisation purity to allow the geostationary orbital position to be shared with a (future) satellite with the orthogonal polarisation. Depending on the outcome of frequency coordination, dual polarization might be considered. Q3. Please give an estimate of the polarisation purity 3

6 2.5. Payload Performance The satellite payload equipment and antennas shall be designed to provide the following characteristics in terms of receive sensitivity G/T and radiated power EIRP: G/T: EIRP: [7 db/k] [50 dbw] G/T The antenna coverage areas specified will to a large extent determine the G/T that can be obtained. The noise temperature shall include radiation from the earth and the industry is invited to make reference to the earth brightness model applied. Q4. Information about LNA dynamic range and the possibility of saturation by jammers is of interest. Is there a trade-off situation between payload G/T on one hand and LNA nonlinear behaviour on the other hand? EIRP Each transponder has one TWTA and some other RF circuits, and more than one transponder is connected to a specific antenna - hence a frequency selective output multiplexer (OMUX) is needed. All X-band TWTAs will have the same saturation power. However, different power values may be of interest to tailor the payload to the spacecraft bus capabilities. Q5. It is expected that state-of-the art OMUXes, antennas and other microwave circuits are used to implement low loss output section for the payload. Could you please comment on this? 2.6. Frequency Plans Channelisation of Uplink Spectrum The X-band uplink frequency spectrum GHz shall be divided into 8 uplink (U/L) channels as shown in Figure 2(a), where RHCP is utilised. Channel bandwidth is 25 MHz. Note the narrow guard band of 2 MHz between two uplink channels that are paired together. Channelisation of Downlink Spectrum The X-band downlink frequency spectrum GHz shall be divided into 4 downlink (D/L) transponders as shown Figure 2(b), utilizing LHCP. The transponder bandwidth is 52 MHz. 4

7 Uplink X-band Channels 24.5 MHz MHz 31.0 MHz 27.0 MHz 37.0 MHz 27.0 MHz 31.0 MHz 27.0 MHz MHz 25 MHz 25 MHz 25 MHz 25 MHz 25 MHz 25 MHz 25 MHz 25 MHz CX1a CX1b CX2a CX2b CX3a CX3b CX4a CX4b PBX1/ PBX2 PBX1/ PBX2 PBX2/ PBX1 PBX2/ PBX1 PBX1/ PBX2 PBX1/ PBX2 PBX2/ PBX1 PBX2/ PBX1 RHCP 7900 MHz 8150 MHz 8400 MHz Downlink X-band Transponders 7250 MHz 7500 MHz 7750 MHz 52 MHz 52 MHz 52 MHz 52 MHz TPX1 TPX2 TPX3 TPX4 PBX1/PBX2 PBX2/PBX1 PBX1/PBX2 PBX2/PBX1 LHCP 38.0 MHz 58.0 MHz 64.0 MHz 58.0 MHz 32.0 MHz Figure 2: X-band channel plans; (a) Uplink channel plan. (b) Downlink transponder plan. 5

8 2.7. Connectivity Plans Uplink Channels to Beam Connectivity Plan The X-band input section shall have flexibility to connect uplink X-band channels to different X-band antennas on channel-by-channel basis as shown in Table 2. An S indicates that the channel is switchable, while S in the table indicates the default connection. Table 2: X-band input section connectivity matrix. Antenna Beams Uplink channels PXB1 PXB2 CX1a S S CX1b S S CX2a S S CX2b S S CX3a S S CX3b S S CX4a S S CX4b S S Downlink Transponders to Beam Connectivity Plan The X-band output section shall have the flexibility to connect downlink X-band transponders to different X-band antennas on transponder-by-transponder basis as shown in Table 3. An S indicates that the channel is switchable, while an X indicates that the channel is fixed wired. An S in the table indicates the default connection. Table 3: X-band output section connectivity matrix. Antenna beams Downlink Transponders PXB1 PXB2 TPX1 S S TPX2 S S TPX3 S S TPX4 S S 2.8. Redundancy and Reliability For all active payload equipment, such as receivers, low-noise amplifiers, down converters, channel amplifiers, linearised travelling wave tube amplifiers (TWTAs) etc.; suitable redundancy schemes shall be proposed Transponder Charectersitics Non-linearity All transponders shall be provided with linearised travelling wave tube amplifiers (TWTAs). TWTAs for which linearisation is a straightforward process shall be selected, avoiding designs that may create nonmonotonic gain transfer curve. 6

9 This is expected to reduce harmful intermodulation products between the user s communication signals. The specification will be in terms of intermodulation between two equal level unmodulated carriers. The lineariser will reduce intermodulation towards that of an ideal soft limiter FGM and ALC Modes It shall be possible to operate any communications transponder independently in a Fixed Gain Mode (FGM), or Automatic Level Control (ALC) mode. The required mode shall be selectable by ground command for each transponder. FGM Mode It shall be possible to command the gain of any communication transponder operating in FGM from ground in gain steps of nominally 1.0 db over a minimum range of 20 db. With a communications channel in ALC mode the gain shall vary in order to provide a constant output power. In the ALC mode the output power shall be adjustable by ground command at least from saturation to 12 db below saturation in steps not exceeding 1 db. ALC Mode The EIRP requirements shall be met when the transponder is adjusted to the maximum output power at which it will be maintained, as a minimum, when the input power flux density reduces by up to 15 db, relative to that required for saturation. For any communications channel operating in ALC mode, the TWTA drive level shall not vary by more than 0.5 db from nominal level when the rate of change of the signal level at the input of the satellite is less than or equal to 1.5 db/second and the absolute level is between the nominal and 15 db below the nominal. The above requirements for FGM and ALC mode of operation shall be met within the defined channel bandwidth for each transponder throughout the entire satellite operational lifetime Passive Intermodulation Passive intermodulation resulting from slight non-linearities in the output network could deteriorate a multi-carrier system. Q6. Please comment on any risk regarding harmful passive intermodulation products (PIMs) in the proposed payload Overload Protection Communication Payload Transponders shall be designed in such a way that the gain of each transponder can be individually and independently adjustable by ground command, in order to drive them into saturation with any flux density within a specific range. For the lowest gain setting, the transponders shall be able to withstand high signal levels, typically in the range db, above the transponder saturation without any payload degradation. Q7. Please comment on thi,,s and suggest a feasible figure? 7

10 Telecommand Links Command receivers shall be able to withstand, without any permanent degradation, high overdrive signals, typical in the range db, in excess of those required for command reception, received from any direction within any receive coverage. Q8. Please comment on this, and suggest a feasible figure? Operational Lifetime and Power Budgets The manoeuvre/operational lifetime of the satellite should be as long as possible, depending on the orbit solution, satellite fuel consumption and launcher selected. Q8. Please give an estimate of the satellite operational lifetime for the different launchers and orbits considered? It is expected that the payload contractor will base all power budgets on TWTAs operating saturated with a single carrier. The operation planned, however, will for some transponders be multicarrier with an output back-off to limit the non-linear distortion Ground Control Segment The Ground Control System (GCS) includes Telemetry, Tracking, Command and Ranging (TTCR) stations, Satellite Control Centre(s) (SCC) and the necessary communication links between the sites. The GCS is the set of facilities in charge of controlling and monitoring the satellites, from the operations handover up to the completion of their injection in the graveyard orbit, which determines the end of the mission. GCS configuration handles the reception of continuous satellite telemetry, spacecraft commanding, ranging and tracking in order to provide information about health status and satellite positioning. 3. Tactical Capacity (UHF) In this section you are invited to describe an UHF capacity, for which you should provide the additional costs (delta cost) due to increased payload items, platform items and launch mass. Please suggest an UHF capacity with the following technical specifications: 1. One (1) satellite beam covering the operation area of interest defined as the Norwegian mainland as well as the sea areas from 40 W to 40 E, northwards from 20 N in the North Sea up to the North Pole. 2. Six (6) channels of 25 khz. 3. Each channel shall be tuneable to five (5) sub-channels of 5 khz. 4. The proposed solution shall be interoperable with NATO UHF satellite communications. Q9. Please provide figures for G/T and EIRP for the UHF transponders that can be achieved using available technologies Q10. Please provide cost impact figures for extending the satellite with the UHF capacity 8

11 Q11. Please comment on any impact on delivery time Q12. Please comment on any impact of the UHF antenna on the platform Q13. Please comment on approaches increasing the robustness of the system to jammers targeting the communication channels 4. Optional Broadband Capacity Extension (X-band) It is of interest to extend the X-band payload capacity with four (4) transponders and two (2) additional spot beams for covering the north-east passage, with the beam characteristics described in Figure 1 and transponder characteristics described in Figure 2. Q15. Please provide the cost impact figures by means of delta cost for this capacity extension. Q16. Please comment on any impact on delivery time END OF DEFINITION DOCUMENT