This part of the NITEOWL proposal was written
by James Giesbrecht, M.Sc., P.Eng.

Note that Section 3 has been revised since the last submission.

NITEOWL Proposal

Part Two

1.  Mission Overview

TBD - JEG

3.  Instrument

3.1 Imaging Spectrograph 

3.1.5  CCD Detector 
	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	
Visible Pixel Array	1024 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	14 bits/pixel	
Frame Transfer Rate	1 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.

3.2  Video Camera for Attitude Determination 
	An analogue video camera will be used to determine the viewing direction of the spectroscopy optics.  The direction the video camera surveys 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 to resolve the direction in which the camera is looking.  Since, the angle between the viewing directions of the camera and optics is known, the vector along which the optics view the starlight can easily be computed.

	The estimated cost for the video hardware is $8,000 (US).  Possible suppliers are Hamamatsu, Panasonic, Xybion, and Bristol Aerospace.  The camera available from Bristol Aerospace transmits its analogue information at 1 MHz or 2 MHz.

3.3  Avionics 

3.3.1  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 limit the operation of standard GPS equipment above an altitude of approximately 18 km and flight speed of 1100 km/hr.  These problems can be overcome with differential GPS equipment.  However, ordinary differential GPS devices will not be suitable either because the NITEOWL project does not permit a communication uplink to the payload.  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 $20,000 ‑$30,000 (US). A possible supplier is Trimble Navigation.  Bristol Aerospace also has a GPS-Telemetry package for approximately $65,000 (Can).

3.3.2  Telemetry system 
	Standard S‑band telemetry will be used to achieve a downlink data rate of 10 Mbits/sec at 10 Hz/bit on a 1.6 GHz carrier.  Bristol Aerospace can supply a GPS-Telemetry package for approximately $65,000 (Can).

3.3.3  Data Rates
	The data rate is expected to be less than 16 Mbits/sec without compression and less than 10 Mbits/sec with compression of 1.7:1.  Compression is necessary to transmit the data collected within the 10 Mbits/sec bandwidth of the telemetry system.  Information rates from data collection and transmission devices are listed in Table 3.3.3.

Table 3.3.3:  Data rates from various sources.
Data Source	Data Rate (Mbits/sec)	
CCD	15	
Temp. and Pressure	1	
		
Total Bandwidth	16	

3.4  Digital and Analogue Hardware 

3.4.1  Compression Electronics 
	A compression ratio of 1.7:1 is required in order to transmit all the data collected by the instrument.  Electronics to perform the compression will consist of standard integrated circuits and logic circuits.  These items can be obtained from various suppliers.

3.4.2  Instrument Power Supply 
	The power supply for the instrument is 30 W at 28 Vdc and 1.07 A.  This capacity is overrated by 25% to allow for a margin of safety.  Power consumption for instrument devices is disbursed as in Table 3.4.2.  Bristol Aerospace can provide a suitable power supply unit.

Table 3.4.2:  Disbursement of power consumption in the instrument.
Device(s)	Power  Consumption (W)	
CCD	1	
Video Camera	4	
Digital and Analogue Electronics	5	
Avionics	2	
In Flight Payload Heating	12	
		
Total Consumption	24	
Overrated by 25%	30	

4.  Other Required Systems

4.3 Radio Frequency Mixer 
	A radio frequency (RF) mixer is needed to mix the analogue video signal onto the 1.6 GHz carrier of the telemetry system.  Depending on the choice of  GPS system it may be necessary to mix the position information onto the carrier as well.  Standard RF mixing circuits can be used to perform this task.  It is expected that the bandwidth of the mixed signal will be less than 105 MHz on a single-side-band (SSB) transmission system.

5.  Required Facilities

5.1 Available Facilities 

5.1.5  SCI-TEC Facilities 
	The facilities, resources, and services available through SCI-TEC are numerous.  These assets include the ordering, purchasing, and collection capabilities of SCI-TEC for instrument parts, the use of computers for instrument control and data analysis, Brewer Spectrophotometer data for reference and correlation with data received from the NITEOWL, space for instrument assembly and storage, and a machine shop.  In addition, SCI-TEC can provide pre-flight instrument testing which encompasses system tests and sub-system tests.  These tests can be undertaken using SCI-TEC’s dark room, optical tables, laser alignment jigs, gas calibration unit (ozone can be generated with this device), and calibrated light source.  In fact, an ozone absorption test can be conducted with these resources.  Finally,  SCI-TEC would be able to employ a few people to perform these tasks.

6.  Instrument and Payload Testing

6.2  Attitude Video Camera Testing and Characterization 
	A comprehensive and conclusive test which characterizes and indicates the correct operation of the video camera will involve aspects of light sensitivity, mechanical strength,  and functionality.  The results of the light test will specify the wavelengths of light for which the camera is useful and the intensities which can be perceived by the camera to obtain a reasonable quality image.  The test on the mechanical strength of the camera will reveal the vibration, stress, and acceleration required to cause the camera to fail.  Finally, a data validity test will determine the capability of the camera to accurately represent the image that it sees in an analogue waveform.

	The sensitivity and intensity tests can be performed by placing a calibrated light source in front of the camera.  By noting the gain response of the camera as wavelength and intensity is varied the sensitivity and intensity properties of the camera become known.

	Mechanical properties of the camera could be determined using standard vibration, compression, and tensile tests and a centrifuge.

	A typical test pattern could be placed before the camera to determine the ability of the camera to represent an image in an analogue waveform.  Comparing the output of the camera with the original image will divulge the accuracy of the image representaion process.

6.3 Determination of Relative Orientation of Imaging Spectrograph and Attitude Video Camera 
	The relative orientation of the imaging spectrograph with respect to the attitude video camera is easy to compute because the viewing directions of both sub-systems lie in the same plane.  Moreover, the angle between the viewing directions is known.  Therefore, the stars surveyed by the camera, when correlated with a star database, will indicate the direction vector for the camera and consequently the orientation of the spectrograph.

7.  Launch and Operational Considerations

7.4  Data Acquisition 
TBD - JEG