Differences

This shows you the differences between two versions of the page.

--- projects:skypod [2011/08/02 02:04] – [SUNSET Skypod] hibby
+++ projects:skypod [2011/08/02 02:22] (current) – [Equipment] hibby
@@ Line 46: / Line 46: @@
 **__Ground Segment:__**
-For all the SUNSET launches, there are two ground stations. One is a mobile unit, one is a satellite tracking    station based at the University of Strathclyde, called STAC.
+For all the SUNSET launches, there are two ground stations. One is a mobile unit, one is a student run satellite tracking station based at the University of Strathclyde, called STAC.
-== STAC ==
+ == Mobile Station ==
-  The primary tracking system for HABs at STAC consists of:
+  * Yaesu FT-817
+  * 12 Element homebrew 'Portable' Yagi antenna
+  * Laptop running the UKHAS special
+  == STAC ==
   * 2 x M2 436CP30 yagi antennas, Vertically stacked, giving an overall gain of 22dBi
   * SSB Electronics masthead preamplifiers
@@ Line 56: / Line 63: @@
   * Dell PC loaded with the relevant UKHAS software of choice
- == Mobile Station ==
-  * Yaesu FT-817
-  * 12 Element homebrew 'Portable' Yagi antenna
-  * Laptop running the UKHAS special
 ===== Telemetry =====
@@ Line 73: / Line 75: @@
   * Battery Voltage
+This was formatted (nearly) to the UKHAS standard and sent back to anyone listening on earth
 ===== Balloon =====
@@ Line 169: / Line 172: @@
 The 3 V solution offered a sufficiently short cut-down time, when compared to the 5 V solution. It was decided to power the cut-down mechanism with the 3 V ancillary power supply as described in power source section. It was decided to keep this separate from the main power supply due to its high current draw (0.55A).
+===== Imaging =====
+===Overview===
+An integral part of the project was the requirement to produce high quality images from within the stratosphere, which meant that the selection and implementation of imaging equipment had to be decided upon in the early stages.
+===Still Images===
+==CHDK – Canon Hack Development Kit==
+An initial idea was to use a Canon camera with high resolution as it is possible to implement code to automatically control the camera. This is known as Canon Hack Development Kit (CHDK) and is well documented online. The first step was to download the correct CHDK auto-build for the camera, which was identified using the Automatic Camera Identifier and Downloader (ACID). From this the firmware version was identified allowing the relevant full build to be found. The final preparatory step was to set up the SD card which was done using software called Cardtricks.
+The process for controlling the camera was as follows:
+  *Find or write a script
+  *Save it onto the SD card (which must be unlocked first).
+  *Re-lock the SD card and replace in the camera.
+The script then ran automatically upon powering the camera. The settings could be written into the script as defaults or adjusted while using the camera.
+For testing purposes a Canon IXUS 55 was used, the relevant software was downloaded and a memory card was prepared. The script required for taking photos at set intervals is known as an intervalometer script and there are many open-source scripts available online. A particularly good script was found which had numerous configurable parameters including:
+  *Delay before the first shot
+  *Interval between shots
+  *Number of photos to take
+  *An option to take photos endlessly
+This script did not work immediately and so was adapted by using sections of another script which did work but had fewer features. This resulted in the final code which was tested and performed as required.
+==Mobile Phone Camera==
+The Sony Ericsson X10 Mini mobile phone which was purchased for tracking had a built-in five Megapixel camera with high quality lens. Various free applications were available for the phone from the Android Store to take photographs at regular intervals. The selected application was called ‘Timerlapse’. Once set up it performed efficiently and effectively in the background, taking high quality photographs at ten second intervals throughout the flight. The application was also programmed to stop taking photographs after four hours, to preserve battery life and phone memory.
+Thus two methods were developed for taking still photographs. Both methods were tested and worked very effectively. However, in order to save on weight and cost only the phone was used to take high quality photographs instead of the CHDK program.
+===Video===
+It was stated in the design specification that High Definition (HD) video footage must be recorded during the flight and so it was required to choose a video camera which could record at a minimum of 720p (1280x720 resolution), but ideally at full HD which is 1080p (1920x1080 resolution).
+The Kodak Playsport was selected because of its waterproofing, high quality images, smaller size and power saving due to smaller screen and dimming.
+=====Heater Circuit=====
+Heating Circuit
+The minimum thermal power output by the circuit was calculated as follows:
+{{http://personal.strath.ac.uk/james.tosh/heatingcircuit_files/image002.gif}}
+This was based on the fact that the camera and phone would not always be charging and only the circuit could be assumed to be always drawing current.
+It was decided intuitively that a heating circuit should generate twice this thermal power to provide sufficient heating for the circuit components. The heating circuit was comprised of many small resistors rather than one central heating resistor. This created a bigger surface area for faster heat dissipation and allowed heat to be supplied directly to each component rather than just the air in the payload. The heating was to be supplied with two AA Energiser Ultimate Lithium batteries supplying a total of 3 V. The required power output was set at 2.5 W, allowing the following calculations to be performed:
+{{http://personal.strath.ac.uk/james.tosh/heatingcircuit_files/image004.gif}}
+This current was achievable, with the Energiser Lithium batteries being capable of 2 A continuous discharge.
+The 3.6 Ω required was created from a network of ten resistors connected in five parallel branches of two series resistors. The individual resistor value required was calculated as follows:
+{{http://personal.strath.ac.uk/james.tosh/heatingcircuit_files/image006.gif}}
+The closest commercially available resistor value was 9.1 Ω leading to the heating resistor network shown in Figure 1.
+{{http://personal.strath.ac.uk/james.tosh/heatingcircuit_files/image008.gif}}
+Figure 1: Heating Resistor Network
+The completed network had the following electrical characteristics:
+{{http://personal.strath.ac.uk/james.tosh/heatingcircuit_files/image010.gif}}
+(I've noticed the maths looks funny. It'll be sorted soon)
+Thus the heating circuit was designed to dissipate 2.473 W of thermal power, with each individual resistor being required to dissipate 0.25 W from 165 mA of current.
+The resistor chosen was RS Product Number: 707-8069 as it had adequate power capacity and a small minimum order quantity as only ten were required.
+===== Flight Analysis =====
+The lovely graphs will be here soon, people.
 ===== Media (Photo & Video) =====