Alphasat TDP#5: Q/V Band Payload

Objectives

The project is finalized to assess the feasibility of realizing one of the Technological Demonstration Payloads (TDP), to be hosted aboard the Alphasat satellite (the main passenger of which will be a proper operational payload). This TDP named Q/V band payload, took the identifier TDP#5. This Phase-A contract, awarded to Space Engineering, has the purpose of providing the technical and planning data needed to evaluate all implications of flying said Q-/V-band payload aboard the Alphasat, in parallel with the main-mission payload. The main objective of the proposed experimental mission is to support three activities:


  • Communications experiments: main aim is to assess, over-the-air, the performance of links operating at Q/V band in conjunction with Interference and Fading Mitigation Techniques (noticeably ACM), in the perspective of deploying future high-capacity systems utilizing that band for the feeder-link (and lower frequency bands for the user-link),

  • Scientific experiment: main aim is to obtain additional Q/V-band propagation data that are indispensable for optimizing modern satellite systems design, and to assess the system-level impact of data coming from propagation measurements, data-bases and channel simulators,

  • Technology experiment: to verify the in-flight performance of innovative hardware, with particular regard to devices based on Micro-Electro-Mechanical Systems (MEMS).

Challenges

Advance in communications and propagation experiments in leading frequency bands.

Benefits

Benefits in terms of Knowledge in the area of modulation, coding and signal fading.

Features

The main objective of the Communications Experiments is to test, in the Q/V bands communication context, the Interference and Fading Mitigation Techniques.

In order to test the ACM technique, a Q/V-band Payload is used for interactive point-to-point communications between two Ground Stations, on the basis of the DVB-S2 standard, which in fact implements the ACM technique. The Receiving Ground Station evaluates the quality of the received signal and communicates this estimation to the other station that consequently modifies the Code and Modulation characteristics (ACM) of the transmitted signal. In such a way the link is dynamically adapted to the propagation conditions.


The functional architecture that allows the performing of this test is shown in Figure 1.  In addition to the Q/V Band payload, two ground stations compliant with the DVB-S2 standard are used. Each ground station is able to transmit to the other station, by means of the satellite, the quality information computed by its own demodulator. Note that in the block diagram of the Ground stations a Noise Generator has been inserted to allow the simulation of worst atmospheric conditions also in a Clear Sky situation.

Figure 1:  Architecture of the TDP 5 Communication experiment


 click for larger image

As it concerns the propagation experiment, the payload will transmit two coherent beacons at Ka and Q band to characterise the rain attenuation behaviour in Tropical and European areas. The beacons reception will be possible using reduced cost terminals.

Plan

The development plan is tailored to Alphasat main Mission Plan. The payload DDP intends to realise the P/L by middle 2008 to integrate it on board the platform.

Current status

The Phase A has been concluded with:


  • preliminary definition of the system specification and architecture
  • Issue of a tentative Interface Control Document towards Alphabus
  • Design and Development Plan definition
  • Schedule proposal
  • Technology Predevelopments preliminary identification
  • Definition of an engineering workplan specific for the Phase B

Contacts

Status date

Wednesday, November 26, 2008 - 12:00