Abstraction Case Study Inquiry Phillip Anderson Jason Schmidt 9/10/2013 Emergent Space Technologies

Statement of Work Enhance GN, SN, and GPS measurement models to simulate higher fidelity tracking data. Abstract out antenna, attenuation, and link budget analysis tools currently available in GPS measurement function and apply to the ground station and TDRSS models. Design and implement architecture for high fidelity modeling that maximizes functionality and reuse. Specific model enhancements shall include: clock and frequency reference modeling, Ionospheric and Tropospheric refraction, antenna phase center bias, component system delays and thermal effects, and time tag offsets. The new models shall be used to generate sample-tracking data from defined reference ephemerides for communication systems testing on future missions.

Statement of Work GPS measurement functionality abstraction. Emergent will research the existing GPS measurement functionality (in gpsmeas) and determine which components are to be abstracted, and develop use cases with assistance from the customer. Two methods of abstracting functionality will then be considered: an object- oriented approach and a direct functional approach. The chosen approach will be implemented first using only gpsmeas, followed by testing to ensure that no functionality has broken. Finally, the abstracted functionality will be implemented into the gsmeas and tdrsmeas functions, and tested to ensure reliability. High fidelity modeling architecture. Emergent will research the existing component models for the components listed in the Subtask k description (clock, atmosphere, etc…). The existing components will be analyzed to determine how they can be generalized to allow for higher fidelity. An object-oriented architecture will be developed that consists of the generic component model capabilities, and requires manual implementation of specific component capabilities. After that, each of the listed components will be implemented using high-fidelity versions of their specific capabilities. Existing low-fidelity component models will be retained for backward compatibility. Finally, Emergent will thoroughly test the new high- fidelity component models with existing test data to ensure accuracy.

Functionality What do you want the measurement models to do that they don’t do already?

Use Cases What use cases would you like to support? Enhancements to GS, TDRS? Link budget?

Measurements What measurements do you need? GPS: range, range rate, doppler, angles, unit TDRSS: ? (do you really want range = (sat- TDRSS) + (TDRSS - GNDstation)) GS: range, range rate, doppler, angles, unit

Errors What (new) errors do you want? – Improved Ionosphere – Improved Troposphere – Improved Charged Particles – Light Time of flight for all measurements – Antenna Phase Center Bias – Transceiver Component Delays – Thermal effects (can we get more specific?) – Clock model on receiver (Requires dynamic model) – Tracking Loop Errors (random noise ~1 meter stdev) – GPS ephemeris errors (both PV and GPS sats clock bias/drift)

Implementation Do you have a preference as to how this is carried out?

What Currently Exists

Format Benefits What's most important to you in terms of abstraction? – Speed? – Flexibility? – Ability to become fully object-oriented?

Abstraction Format (case study) Functional (modify/write code in current style) – Quick runtime – Able to concentrate more on the code instead of making it object- oriented Semi object-oriented – Not as fast runtime – Not as flexible – Transition for future object-oriented efforts Fully object-oriented – Probably not in scope now, future goal – Very flexible – Some object-oriented overhead slows runtime

Functional

Semi-Object-Oriented

Deluxe Object-Oriented