Shuttle Return2 Flight NASA

Shuttle Return to Flight Launch Planning with STK : 

Shuttle Return to Flight Launch Planning with STK Harold Robertson NASA Johnson Space Center, Houston, TX

Shuttle Return to Flight Launch Planning with STKBackground: 

Shuttle Return to Flight Launch Planning with STK Background The loss of the Space Shuttle Columbia during entry on Feb. 1, 2003 was attributed to a breach of the wing leading edge RCC by debris impact The debris source was determined to be a piece insulating foam that came off the external tank (ET) during ascent The first two return to flight missions (STS-114 and STS-121) were designated as test flights to evaluate the changes made to the Shuttle system since the Columbia accident Approximately 39 test objectives were identified for STS-114 (including evaluation of ET changes) Besides engineering analysis, ET assessment after ascent was important in establishing if any debris was liberated that threatened the Shuttle

Shuttle Return to Flight Launch Planning with STKBackground (Continued): 

Shuttle Return to Flight Launch Planning with STK Background (Continued) Daylight launches were baselined for the test flights to maximize usable imagery from ground based assets during ascent Some of the best instrumentation for evaluating the ET is on the Shuttle itself. Shortly after separation, two 16mm movie cameras and a still camera image the tank as it falls away A few moments later the Shuttle performs a pitch up maneuver and the crew uses both a still camera and camcorder to image the tank Orbital daylight was required to again maximize the chances of getting acceptable imagery from these cameras The still cameras were upgraded from 35mm film to digital (Kodak DCS 760) to allow same day downlink of the images

Shuttle Return to Flight Launch Planning with STKLaunch Opportunity Planning Constraints: 

Shuttle Return to Flight Launch Planning with STK Launch Opportunity Planning Constraints STS-114 and 121 are both support missions for the International Space Station (ISS) This requires a launch into an inertial plane at 51.6 deg inclination that allows rendezvous with the ISS The daily launch window to achieve the required rendezvous plane moves about 25 minutes earlier each day due to nodal regression Phase window considerations cause additional small time shifts On an annual basis, roughly 40% of the daily launch windows result in darkness for ascent The post ascent requirements for orbital daylight removes several more days Several times a year, high Beta (angle between the sun and the orbital plane) make Shuttle/ISS attached operations impractical due to thermal management problems and further restricts available launch days

Shuttle Return to Flight Launch Planning with STKLighting Assessment (Initial Approach): 

Shuttle Return to Flight Launch Planning with STK Lighting Assessment (Initial Approach) Legacy mission planning tools were easily able to determine: Daily planar launch window and rendezvous phase window times Beta angle Ascent and post ascent lighting The toolset had no easy way to assess the acceptability of the post ascent lighting Other software could generate highly precise CAD views and exact lighting conditions, but required considerable data preprocessing and setup for each day analyzed STK proved to be a useful tool to assess the post ascent lighting and screen available launch days The initial setup was to import the trajectory and attitude files from a powered flight ascent simulation for a given launch date and time. The Shuttle and ET were each modeled as separate satellites STK sensor tools were used to create camera sensors that allowed modeling each camera’s field of view This setup worked well, but required a unique scenario build and trajectory files for each launch date evaluated

Shuttle Return to Flight Launch Planning with STK Post Ascent Lighting Assessment (Refined Approach): 

Shuttle Return to Flight Launch Planning with STK Post Ascent Lighting Assessment (Refined Approach) To avoid having to manually creating multiple scenarios, a few simplifications allowed rapid generation of lighting conditions for each theoretical launch day of the year. 1st simplification – even though the Shuttle is flying to a unique inertial plane for a rendezvous mission to ISS, the groundtrack shift across the 5 to 10 minute launch window is small. Liftoff was assumed to be at the same point in the launch window (coplanar). This potentially introduced a small spatial error. 2nd simplification – chose to ignore the phase window and set the time relative to the daily 25 minute shift (earlier) of the planar window (introduces a small temporal error) These two simplifications allowed the Shuttle and ET to be modeled as facilities (static objects) fixed at the points along their trajectories where the photos would be taken. The small errors introduced by the assumptions were considered acceptable with regards to lighting evaluation. The only time dependent variable left in the problem was the sun position. A new scenario was constructed which modeled the Shuttle Orbiter and ET as STK “facilities” A representative trajectory (such January 1, 2005) was used to establish the Shuttle and ET facility locations and attitudes just after separation when the umbilical camera photography starts This was repeated in a separate scenario that located the “static” positions of the Orbiter and ET at the start of crew photography

Shuttle Return to Flight Launch Planning with STK Sample Image Output: 

Shuttle Return to Flight Launch Planning with STK Sample Image Output The scenario timestep was set to 23 hours and 35 minutes (causing each frame to be 25 minutes earlier than the previous day) The software VCR module was utilized to generate a series of bitmaps (one for each launch opportunity) for the entire year Each bitmap image (or movie frame) represented a sample photo associated with the daily rendezvous plane launch window The images were then analyzed by JSC photo interpreters to evaluate the lighting This involved assessing key areas of the tank to see if that area was lit or in shadow The samples were posted on in internal website that allowed mission planners to see for themselves which days had adequate lighting

Shuttle Return to Flight Launch Planning with STK Areas of Interest on the ET and Sample Image Assessment: 

Shuttle Return to Flight Launch Planning with STK Areas of Interest on the ET and Sample Image Assessment

Slide9: 

Shuttle Return to Flight Launch Planning with STK Analysis – Umbilical Well and Crew Camera Lighting Good lighting for ET umbilical well photography requires the sun overhead or in the west. Good lighting for crew handheld photography requires the sun overhead or in the east. Result: Few dates provide good lighting for both umbilical and crew handheld photography. (STS-114 had good lighting for both on Jul 26, 2005)

Shuttle Return to Flight Launch Planning with STKResulting Launch Opportunities for STS-114: 

Shuttle Return to Flight Launch Planning with STK Resulting Launch Opportunities for STS-114 Umbilical camera photography was selected as “prime” in establishing the launch windows Launch periods for 2005 that met all constraints: March 16 to April 1 May 15 to June 3 July 13 to August 1 (STS-114 launched on July 26) September 9 to September 25 November 7 to November 10

Shuttle Return to Flight Launch Planning with STK Comparison with STS-114 Imagery: 

Shuttle Return to Flight Launch Planning with STK Comparison with STS-114 Imagery For the umbilical camera photos: Unmodeled yaw rate in the tank produced a slight offset For crew photography: There is no accurate preflight prediction of the ET attitude Times are approximate, based on internal camera clock The STK camera sensor was set up to boresight the ET model, so there were no framing issues. The actual photographer had to manually acquire and frame the ET in the viewfinder

Shuttle Return to Flight Launch Planning with STKSupplemental Analysis – Umbilical Camera: 

Shuttle Return to Flight Launch Planning with STK Supplemental Analysis – Umbilical Camera A detailed study was later conducted to see the lighting trend for the entire year The timestep advance was set to one minute. The view was manually stepped forward/backward to establish acceptable lighting boundary times for a couple of days each month The actual launch window times were ignored in this analysis

Shuttle Return to Flight Launch Planning with STK Additional Support : 

Shuttle Return to Flight Launch Planning with STK Additional Support Once built, the STK setup was used to generate several illustrations and videos for management presentations, crew training and Public Affairs

Shuttle Return to Flight Launch Planning with STK Summary: 

Shuttle Return to Flight Launch Planning with STK Summary STK allowed rapid generation of sample imagery for lighting analysis. New sets could be produced quickly when mission inputs changed. Greatly reduced the number of higher fidelity image program assessments required The STK 3D views and video clips allowed development of easy to understand presentations on the ET lighting topic