NITEOWL Risk and Reliability

This section addresses aspects of the NITEOWL Risk and Reliability Assessment. The primary focus will be on a risk analysis of the various subsystems associated with the instrument and the mission. The reliability of these subsystems will, for the most part, be determined by the sub- contractors involved in the implementation of each component.

The entire payload will undergo acceptance tests appropriate to determine the suitability of the systems and subsystems. These will be undertaken in cooperation with the sub-contractors involved or the industrial partner. It has been determined that at this point in time, there can be no provision for redundancy in the flight subsystems in the experiment due to cost constraints.

The general categories for risk and reliability analysis are discussed below.

Science: The major concern here, and one that will have a major impact on the success of the project, is overlooking some aspect(s) of the experiment that would lead to failure. This can be mitigated by close scrutiny of all aspects of the experiment as well as outside review. Possible areas of concern are: incorrect assumptions, error in modeling, simulation.

Pre-Launch: Since a number of the subsystems will be sub-contracted, it is important to monitor closely the specification, delivery, and documentation associated with these subsystems. This is included in the management plan for the project. A major mitigating consideration is that the launch window can be over a number of days each month allowing (to some extent) delivery dates to slip. This will, however, increase the cost of launch. Possible areas of concern are: failure to meet schedule, faulty design, payload weight, destructive testing, incomplete documentation

Launch: The launch of the payload will be coordinated by Bristol Aerospace and Akjuit . They will be responsible for all aspects of the launch operation and initial manual tracking/capture. Possible areas of concern are: vehicle failure, manual tracking failure, bad weather, safety conditions.

Vehicle Dynamics: It is necessary to have the vehicle slowed by parachute and have a stabilized (spin rate of 1 rpm and a swing amplitude < 5°) flight. Areas of concern are: parachute deployment, de-spin.

Optical System: It is possible for the optical system to become damaged or mis-aligned during the launch portion of the experiment. The mounting and alignment of this system will have to be checked during manufacture and assembly. Possible areas of concern are: G forces, vibration, grating failure, stray light.

Electronic Systems: This will include the power supply, compression hardware, and miscellaneous monitoring circuitry. Possible areas of concern are: incorrect power estimates, incorrect interfaces, physical failure, EMI , thermal problems. Outside expertise will be accessed whenever appropriate.

On-Board Data: The major component of this system is the data compression hardware subsystem. Since this will not be a commercially available unit, past performance of the system is not available for analysis. Areas of concern are: incorrect compression ratio, GPS subsystem failure, antenna failure.

Ground-Based Data: Aspects of this area include telemetry, data recovery and data storage. Areas of concern are: power failure, software failure, recorder failure, antenna failure.

Post-Flight: This aspect is related to the recovery of the payload. Possible areas of concern are: on-board data storage (if used) is lost, payload is lost.

In determining the "risk" involved with each of these mission aspects, the following were considered:

System Risk Level - depends on knowledge and experience with each particular system

Low:	Use of flight qualified system, well understood considerations and methods

Medium:	Possibility of error, incorrect specification

High:	New systems, inexperience, inherent risk

Probability of Occurrence - depends on how successful each subsystem has been in past missions

Low, Medium or High based on past experience, reliability and input from team leaders.

Impact on Mission - depends on how a problem with each subsystem affects the mission

Low:	Threatens optimal success

Medium:	Threatens schedule or acceptable success

High:	Threatens cost or minimum success

Difficulty in Mitigating - depends on whether a problem with the subsystem in question can be resolved and what else can be done if this is not possible

Low:	Well understood approach to minimize/identify/correct problem

Medium:	Some opportunity to minimize/identify/correct problem

High:	No opportunity to minimize/identify/correct problem

Based on the assessment of each system (summarized for illustrative purposes in the table below), an aggregate averaging has made it possible to rank each mission aspect according to the risk level associated with it. From highest to lowest risk:

1.	Launch

2.	Vehicle Dynamics

3.	Optical System

4.	On-Board Data

5.	Electronic Systems

6.	Ground-Based Data

7.	Science

8.	Pre-Launch

9.	Post-Flight

The launch and the vehicle dynamics are the two riskiest aspects. However, given that the payload survives the launch and is put in a position to begin taking data, we are quite confident that the rest of the mission will be successful.

Shown below is a summary of the risk level estimations for some of the key issues associated with each mission aspect heading discussed previously.

Mission Aspect	System Risk Level	Probability of Occurrence	Impact on Mission	Difficulty in Mitigating
Science
Initial instrument design faulty or not proven	Medium	Low	High	Low
Scientific variable assumptions not correct	Medium	Low	High	Low
Pre-Launch
Improper testing	High	Medium	Medium	Low
Parts are unavailable or aren't received	Medium	Medium	Medium	Low
Launch
Invalid initial trajectory	High	Medium	High	High
Vibration during launch causes wires to break or intermittent connections	High	Medium	High	High
Vehicle Dynamics
Parachute deployment	High	Medium	High	High
De-spinner doesn't deploy	High	Medium	High	High
Optical System
Instrument optics misaligned due to mounting tolerances	Medium	High	High	Medium
Stray light in instrument	Medium	High	High	Low
Electronic Systems
Problem turning instrument on at apogee	Medium	Medium	High	Medium
Subsystem interfaces not correct	Medium	High	Medium	Low
On-Board Data Handling
Data compression hardware failure	Medium	Medium	Medium	High
Antennae failure	Medium	Medium	High	High
Ground-Based Data Handling
Antennae failure	Medium	Medium	High	Low
Power failure	Medium	Medium	High	Low
Post Flight
Vehicle recovery	High	Low	Low	Low