The goal to be achieved within this project is to demonstrate the feasibility of Advanced In-Orbit Testing concept based on the following objectives:
- In-Orbit Test time reduction: Depending on the satellite architecture an IOT campaign can extend over a period of a couple of weeks and even more in some cases. An IOT campaign driven by and Advanced In-Orbit Test System (AIOTS) should only take few days.
- Accuracy: As a main objective, accuracy testing will not be sacrificed by the testing duration reduction.
- Spin Off: Additional applications for the final product can be ESVA testing as well as Traffic Monitoring without major modifications.
- Drift Orbit: Testing during drift orbit should also be possible with the final product.
The key issue of Advanced IOT concept is the selection of efficient stimulus signal and the use of Digital Signal Processing Techniques what allows to reduce in-orbit test time without scarifying accuracy.
Satellite in-orbit testing is an expensive task and customers push IOT engineers to speed up testing phase just to put the satellite in service as quick as possible. This is just the main benefit of AIOTS; 'the spacecraft will be operational very quickly following an identical test plan and maintaining the same accuracy level as the traditional IOT systems'
A classical IOT system architecture is shown in the following figure. In principle, this architecture is still valid for an AIOTS because what produces a significant advance are the methods, as well as new instruments.
Figure 1: Classical IOT System Architecture
Traditionally, IOT methods have been based on classical rack-and-stack lab instrumentation. New families of instruments based on powerful digital signal processing capabilities are now emerging; AIOTS makes use of this kind of COTS instruments.
Measurement equipment with friendly and complete front panel giving to the user a direct way to access all their functionalities are conceived to be used mainly in a lab environment where the interaction with the operator is something that can be done quite often. However, AIOTS is in fact an Automated Test Equipment (ATE) where the software application in charge of running the In-Orbit Test procedures is designed in such a way that local operation is not normally needed.
This is a weighty argument to propose instrumentation based on the VXI, PCI, CompactPCI or PXI buses. This kind of instruments provides a very high level of integration, as well as performance in terms of speed, acquisition, data transfer rates and functionalities. The art state of this technology offers a complete range and diversity of instruments covering from sources, vector signal analysers, digitisers, meter, tuners, switching devices, ...
All above considerations guides to the AIOTS architecture shown in the figure below, where there is a noticeable reduction of hardware in favour of software compared to classical IOT System.
Figure 2: AIOTS Architecture
The result is a powerful Advanced IOT Bench able to cope with different satellites and IOT station architectures, meeting the integration and flexibility requirements
The tasks within this project are performed in three different stages.
The first stage is focused on the definition, specification and design touching aspects such as:
- Asses the in-orbit testing environment
- Critical analysis of the current test methods used by different satellite manufacturers and carriers.
- Study of Advanced IOT techniques and Procedures
- IOT Bench Hardware and Software Design
The output of this stage is the production of the Design Review Documentation.
The second stage pursuits the development of an Advanced IOT Bench that will not incorporate all functionalities asked for a complete or final product but limited to the ones considered as relevant or not accessories. During this phase, some trials are exercised over a real environment and simulator in order to reassess the design.
Finally, the last stage demonstrates the performances of the IOT Bench at factory and in a real environment using existing facilities.
The original tasks have been completed successfully and an extension of the work has been agreed; Indra shall develop and include a calibration system in their developed product, in order to offer to their potential customers a more complete system.
The following items will be developed and integrated:
1st stage up-converter 70MHz to L-band,
Flexible 2nd stage up-converter L-band to Ku-band,
Power measurement system.