European Space Agency

Low Mass Output ONET Assembly

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Objectives

The main objective was to design, manufacture and qualify an L-Band Onet and filters, and to have a complete assembly fully qualified.

To have the chance of selling this product in the commercial market RYMSA needed a competitive advantage from their competitors. Our competitive advantage for this product was to have the Alphasat payload specification from Astrium UK, trying to comply with this specification with the minimum mass and size.

Challenges

Once the design was completed the activity was stopped due to certain technical limitations, not compatible with the Alphasat program target. These limitations came mainly from the mechanical side in terms of dimensions and mass. In detail:

  1. In order to reduce the overall length of the L-band ONET assembly, the inner conductors were bent from the originally flat configuration, so that they were located in three different housings separated by two laminas. From the mechanical point of view this configuration was very complex in terms of construction and assembly.
  2. For EMC reasons, the ONET matrix should be properly sealed, so it required a large number of screws. However there was not always free access area to host the screws externally because sometimes the outer conductor of one of the layers was too close to the outer conductor of the next layer. For this reason, some screws would have to be accommodated internally (thickenings in the intermediate slide), complicating largely the assembly.
  3. The L-band ONET Assembly is big equipment, the current model weighing nominally 7.81 Kg. One of the aims of this program was to reduce the mass having positive MOS in all the parts of the ONET Assembly. However, this was a complicated task because of the large number of screws required and the thermal treatments (weight of silver and paint).

Considering the previous issues, a minimum thickness was defined to complete the mechanical analysis. The total weight considering this thickness resulted in 7.1 Kg. However, negative Margins of Safety were obtained with this configuration, and therefore the wall thickness had to be increased, obtaining a total mass of around 7.8 Kg.

This number was overpassing by far the Astrium requirement, which was 5.5 Kg. Different solutions were investigated to solve this point (use of magnesium, screws reduction, etc) but none of the alternatives was selected. For this reason, the activity has been stopped after holding the CDR.

Benefits

To have the chance of selling this product in the commercial market RYMSA needed a competitive advantage from their competitors. Our competitive advantage for this product was to have the Alphasat payload specification from Astrium UK, trying to comply with this specification the minimum mass and size.

Features

The equipment is a 8x8 High Power Passive Matrix made in bar-line technology. Passband filters are placed at every input to reject frequencies out of the specified range, and test couplers at the outputs extract signal samples to verify the proper behavior of the matrix.

The function is to combine, with low loss, 8 coherent input signals into one of 8 output ports depending on the input signals phase sequence. Thus, there are 8 modes of operation. A mode is defined as a unique set of phase weights that, applied to each of the 8 input signals, directs all the power to one of the outputs.

Plan

RYMSA selected the most competitive implementation for the space market (low mass and dimensions) with adequate performances. The new design must be able to introduce the input filters and the output couplers. The filter was the critical element in order to guarantee the stability performances (phase and amplitude) of the complete assembly. Therefore, the proposed design included the thermal stabilization to assure phase tracking in worst case, when filter temperatures can be different according to their allocation with respect to the panel interface.

Current status

A Breadboard of the filter was manufactured, obtaining results very near to the ones foreseen by analysis.

The activity has been stopped after CDR as the current design is not adjusted to the targeted power requirements of the market. An alternative using strip-line technology for the ONET seems to be more adequate.

Contacts

Status date

Tuesday, May 17, 2011 - 16:47