2.2  Video Camera for Attitude Determination

	A video camera is needed so that the viewing direction of the instrument can be determined.  The video camera will be set at a known angle with respect to the spectroscopy optics.  Star images that the camera produces will be correlated with a star database so that the viewing direction of the spectrographic equipment can be computed.

	The estimated cost for the video hardware is $8,000 (US).  Possible suppliers are Hamamatsu, Panasonic, and Xybion.

2.3  Avionics

2.3.1  Global Positioning System

	A Global Positioning System (GPS) device is required to track the position of the instrument as it goes up and as it comes down. The position of the payload must be known for two reasons: 1) so that a measurement taken by the instrument can be associated with a specific position above the earth; and 2) so that the payload can be recovered.

	Constraints imposed by the US government on suppliers of GPS hardware can be overcome with differential GPS equipment. However, since the NITEOWL project does not permit a communication uplink to the payload ordinary differential GPS devices will not be suitable. Instead, inverted differential GPS hardware will be used. Inverted differential GPS hardware requires a standard GPS receiver in the payload, a communication downlink from the payload, and a base station.

	This type of GPS equipment will estimate the position of the payload within 1m. The cost of the hardware will be approximately $10,000 ‑ $20,000 (US). A possible supplier is Trimble Navigation.  Bristol Aerospace also has a GPS-Telemetry package for approximately $65,000 (Can).

2.3.2  Telemetry system

	Standard S‑band telemetry will be used to achieve a downlink data rate of 10 Mbits/sec.  The carrier is 1.6 Ghz with a bandwidth of 160 Hz/bit.  Bristol Aerospace will supply a GPS-Telemetry package for approximately $65,000 (Can).

2.3.3  Data Rates

	The data rate is expected to be 117 Mbits/sec without compression and 9.75 Mbits/sec with compression of 12:1.  Compression is necessary to transmit the data collected within the
10 Mbits/sec bandwidth of the telemetry system.  Information rates from data collection devices are listed in Table 2.3.3.

Table 2.3.3:  Data rates for various instrument devices.
Device	Data Rate (Mbits/sec)	
CCD	25	
Video Camera	91	
Avionics	1	
		
Total Bandwidth	117	

2.4  Digital and Analogue Hardware

2.4.1  Compression Electronics
	A compression ratio of 12:1 is required in order to transmit all the data collected by the instrument.  Electronics to perform the compression will consist of specialized integrated circuits and logic circuits.  These items can be obtained from various suppliers.

2.4.2  Instrument Power Supply

	The power supply (unit provided by Bristol Aerospace) for the instrument is 45 W, at
28 Vdc and 1.6 A.  This capacity is overrated by 50% to allow for a margin of safety.  Power consumption for instrument devices is disbursed on the following basis:

Table 2.4.2:  Power consumption versus device in the instrument.
Device(s)	Power Consumption (W)	
CCD	1	
Video Camera	4	
Digital and Analogue Electronics	5	
Avionics and Telemetry	5	
In Flight Payload Heating	15	
		
Total Consumption	30	
Overrated by 50%	45	

3.1.5  CCD Array

	Light collected by the optics will be focussed onto a charge‑coupled device (CCD) so that the spectral images captured by the CCD can be used to determine properties of ozone above the earth.  To adequately accomplish this task the characteristics of the CCD must be known.

	The CCD imager will have the nominal specifications shown in Table 3.1.5.

Table 3.1.5:  Nominal specifications for the CCD imager.
Characteristic	Specification	
Pixel Array	1024 x 1024	
Visible Array	512 x 1024	
Pixel Size	24 um x 24 um	
Potential Well Depth	300,000 electrons	
Quantum Efficiency	55% - 85%	
Wavelength Sensitivity	400 nm - 900 nm	
Imaging Size	24.6 mm x 24.6 mm	
Resolution	12 bits/pixel	
Frame Transfer Rate	4 frames/sec	
Exposure Time	1/30 sec to 5 min	

	Science‑Tech, a Canadian company, can provide an intensified CCD (ICCD) for $28,000 (Can). K‑Space Associates Ltd. can supply a CCD for $3,500 (US).  Scientific Imaging Technologies, Inc. can also provide a large area CCD.