SEDSAT-2 Ground
From SEDSWiki
This is the page for the SEDSAT-2 Ground Control team. Ground Control design notes are filed in Category:SEDSAT-2 Ground. There is also a categorised overview of Ground team design notes.
Contents |
Team
The Ground team is made up of members in Bath (UK), Sherbrooke (Canada) ,Trichy(India) and Vellore(India).
Lead
Andrew Bacon (Bath,UK) - droidus@gmail.com
[Second] Talini Pinto Jayawardena (Bath,UK) - talinij@hotmail.com
Members
(add your name here, and include a link to your protoforge user page!)
P.Kalaiarsi (NIT-Trichy,India)
Kunal Sharma(VIT-Vellore,India)
Team status
This is a list of things the Ground team is currently working on. To edit the list, click here.
Tasks as of 5th July 2008:
- Everyone should join the Ground Team Google Group to share any work in progress with other Ground team members
- Everyone to make sure they are able to chat using Google Talk
- add droidus@gmail.com in GTalk to be able to join meetings
- Think about what areas you are interested in working on
- email Andrew or Talini, who will be happy to assign you a task or talk about your ideas
- Have a look at the tasks described in Pre-Design Phase to see if you can help:
Pre-Design Phase
- Read through Ground Station design note at: http://wiki.seds.org/index.php/SEDSAT-2_Ground_Design_Notes_20080329
- if you have any questions on this then feel free to e-mail Andrew or Talini
- any comments/ideas about this: post on a relevant thread on the google group, or start a new one!
- Research what other cubesat ground station teams have done
- there is a list of cubesat teams here: http://en.wikipedia.org/wiki/Cubesat
- post any findings on the google group, or email them to Andrew
- there is a list of cubesat teams here: http://en.wikipedia.org/wiki/Cubesat
Design Phase
- A technical specification for the Antenna can be found here:
- P.Kalaiarsi has published research into Antenna Mounting Rotators
- this can be found here: http://wiki.seds.org/index.php/SEDSAT-2_Ground_Design_Notes_20080601
- Kunal Sharma has prepared the notes on GENSO(Global Educational Network for Satellite Operations).
- this can be found here: http://wiki.seds.org/index.php/SEDSAT-2_Ground_Design_Notes_20090820
- Here is a summary of the three different ground station designs, including costing:
Expanding on this research leads to four plausible antenna set ups:
- 1) Parabolic Antenna
- A single elevation and azimuth (el-az) rotator anchors the dish to a stand. The rotator controller (represented by a box with a dial) allows for manual and computer control.
- Advantages: A simple and traditional design that has an exponential increase in gain for a small increase in diameter.
- Disadvantages: The dish will be costly and have a large ground footprint. The rotator will need to be capable of handing the weight in windy weather.
- 2) Yagi Array Antenna
- An array of medium gain Yagi antennas are clustered together such that the signal can be electronically steered several degrees from the axis by modifying the polarisation. A single el-az rotator is needed for tracking across the bulk of the sky.
- Advantages: Extremely high accuracy, and therefore an exceptional signal-to-noise ratio.
- Disadvantages: The most complicated of the four designs, expensive controllers will need to be bought or designed. It is likely that a custom mount will be needed, as well as a large rotator to move the assembly.
- 3) Separated Low and High Gain Yagi Antennas
- A low gain / wide field antenna is used as a 'range finder' to scan a large patch of sky to find the position of the satellite. A second high gain / narrow field antenna will then use the position to communicate with the satellite. Both antennas can be rotated independently or in a 'slaved' mode where one will follow the other. These modes are accessed through a switch which selects the destination of the rotator controller output.
- Advantages: As either antenna can be used independently, this provides some redundancy to the system (although the wide field would have troubles communicating on its own, and it might be difficult to find the satellite only using the narrow field).
- Disadvantages: To be able to operate independently without colliding, both antennas will need to be placed a distance apart; this will make attaining planning permission harder and might require adjustments to make sure they are both pointing at exactly the same area of sky.
- 4) Combinded Low and High Gain Yagi Antennas
- To overcome the problems of separation, both antennas can be connected to a single mount and rotator that would move both in tandem. A second high accuracy el-az rotator can be added to the high gain / narrow field antenna to allow fine adjustments to increase the signal-to-noise ratio.
- Advantages: The ground footprint is half that of the separated antenna design, making planning permission easier to get. A potentially higher degree of accuracy than the separated design can also be achieved.
- Disadvantages: The low gain / wide field antenna can still be used in the event of narrow field antenna failure, but the narrow field could not be used in the event of wide field failure as the two antennas would collide. This does not provide a full redundancy, unlike the separated antenna design. Also two rotator controllers will be need to achieve high accuracy whilst tracking, adding to the cost.
- Steve from Comms Team has contributed a diagram showing a sensible configuration of the Ground Station hardware.
- Any counter-designs or comments on this should be expressed on a thread in the Google Group.
