Ka band high performance reflectors activities aimed to provide the evolution from the standard C / Ku reflectors to Ka band ones in order to implement them on the first commercial Ka Mission awarded to CASA, Eutelsat: Ka Sat Satellite.
The Ka band reflectors technology was successfully proven in the frame of previous ESA programs such as HYLAS and NG reflector, but it´s application for big communication reflectors required the help of the current program, for its implementation aboard Ka Sat.
The Ka Band High performance Reflectors for Broadband Services program consisted of all the trade offs, design and analysis, including qualification of materials and processes needed to manufacture the first Ka Sat program (Reflector manufacturing activities were excluded), and go through the subsequent reflector qualification testing, to ensure it´s applicability aboard Ka Sat.
In order to achieve this, the Ka band high performance reflectors activities were divided in two steps:
- A study proposal on which preliminary reflector design and analysis were conducted, including development testing for high temperature adhesives, comprising as well development test samples. This phase, already concluded, allowed the next one to start,
- A full proposal that comprised the reflector detailed analysis, and the preparation of the test procedures, testing and reports of the first Ka band reflector made.
This phase also included the material qualification of the first non specular sunshield required to avoid heat concentration over the S/C satellite walls.
A picture of the first Ka Sat reflector made and tested in accordance with the contents of the program, and a comparison of the specular and non specular sunshield material is shown below.
For the reflector itself the main key issue was the design and analysis of the largest Ka Band metalized reflector for telecommunication purposes made in Europe.
Due to the dual deployment and volume constrains the backing structure height was reduced with respect to the standard ones, to accommodate in a reduced space both reflectors including their respective sunshields.
Another constrain was the sunshield itself. Standard sunshield material are specular and this means than due to the big reflector dimensions, reflection over the S/C walls produced big heat concentration.
To avoid this, the surface of the sunshield was treated to eliminate its specularity while maintaining the Thermooptical and surface resistivity properties.
The main benefit obtained through the activities conducted within this program was the capability to anticipate to the foreseen problems during the manufacturing of the four Ka Sat reflectors.
The results obtained, through the qualification of the reflector enabled EADS CASA to have the technology to be a reference in Ka Band reflectors.
In addition, all the experience gained was later applied in similar commercial Ka band programs, the most representative ones being Arabsat 5C and Yahsat to be launched within this year.
The reflector design is composed of the following sub-assemblies:
- A reflector dish (unshaped) and its associated backing structure,
- Interface stiffener box and brackets for ADTM,
- Interface for HRM fixation (4 points),
- Alignment devices, handling and lifting inserts,
- Thermal control hardware,
- Sunshield and sunshield supports,
- Grounding devices.
Reflector parabola geometry can be found below.
A picture of its main constitutive items is hereafter provided.
The reflector was later on submitted to the following test campaign comprising the corresponding test procedures and associated test reports.
|1. 3D Machine Surface Measurement||EADS CASA ESPACIO Madrid, Spain|
|2. I/F Measurement||EADS CASA ESPACIO Madrid, Spain|
|3. Mass Measurement||EADS CASA ESPACIO Madrid, Spain|
|4. Ambient Pressure Thermal Cycling||Intespace|
|5. Thermal Vacuum Cycling||Intespace|
|6. Thermoelastic in Vacuum||Intespace|
|9. Grounding Measurement||Portable Equipment|
At this phase, it was as well qualified the non specular sunshield material that later on was used to made the flight sunshields.
The following flow illustrates the tests made.
The project plan can be found below. As mentioned before, the study phase provided the required inputs to the full proposal in terms of reflector preliminary design and analysis activities including high temperature film adhesive material qualification activities.
The full proposal phase included the final reflector design and analysis activities and the first Ka Sat qualification testing, as well as the sunshield material qualification.
Ka Sat was successfully launched and in accordance with EADS CASA Espacio is currently working at full customer satisfaction.
There exist prospectives for a second Ka Sat satellite, which is at the moment in the early mission definition phase, awaiting to confirm the demand on the use of wireless internet services