SPHERES flight operations testing and execution The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation Mohan, Swati, Alvar Saenz-Otero, Simon Nolet, David W. Miller, and Steven Sell. “SPHERES Flight Operations Testing and Execution.” Acta Astronautica 65, no. 7–8 (October 2009): 1121–1132. As Published http://dx.doi.org/10.1016/j.actaastro.2009.03.039 Publisher Elsevier Version Author's final manuscript Citable link http://hdl.handle.net/1721.1/99453 Terms of Use Creative Commons Attribution-Noncommercial-NoDerivatives Detailed Terms http://creativecommons.org/licenses/by-nc-nd/4.0/ IAC-07-A2.6.03 SPHERES Flight Operations Testing and Execution Swati Mohan Graduate Student, Massachusetts Institute of Technology, Cambridge, MA USA [email protected] Dr. Alvar Saenz-Otero Research Associate, Massachusetts Institute of Technology, Cambridge, MA USA [email protected] Dr. Simon Nolet Post-Doctoral Associate, Massachusetts Institute of Technology, Cambridge, MA USA [email protected] Dr. David W. Miller Professor, Massachusetts Institute of Technology, Cambridge, MA USA [email protected] and Steven Sell SPHERES Project Manager, Payload Systems Inc., Cambridge, MA USA [email protected] Abstract SPHERES (Synchronized Position Hold Engage Reorient Experimental Satellites) is a formation flight testing facility consisting of three satellites operating inside the International Space Station (ISS). The goal is to use the long term microgravity environment of the ISS to mature formation flight and docking algorithms. The operations processes of SPHERES have also matured over the course of the first seven test sessions. This paper describes the evolution of the SPHERES program operations processes from conception to implementation to refinement through flight experience. Modifications to the operations processes were based on experience and feedback from Marshall Space Flight Center Payload Operations Center, USAF Space Test Program office at Johnson Space Center, and the crew of Expedition 13 (first to operate SPHERES on station). Important lessons learned were on aspects such as test session frequency, determination of session success, and contingency operations. The paper describes the tests sessions; then it details the lessons learned, the change in processes, and the impact on the outcome of later test sessions. SPHERES had very successful initial test sessions which allowed for modification and tailoring of the operations processes to streamline the code delivery and to tailor responses based on flight experiences. 1. Introduction to SPHERES The SPHERES project, Synchronized Position Hold Engage Reorient Experimental Satellites project, is a formation flight testbed operating inside the International Space Station (ISS) developed by the Massachusetts Institute of Technology (MIT). The objective is to provide a fault tolerant environment to perform cutting Figure 1: SPHERES satellites aboard the ISS edge research for algorithm development in fields such as estimation, docking, formation Aboard the ISS, SPHERES consists of three flight, reconfiguration, fault detection and path identical satellites, a laptop computer ground planning. station, and a radio frequency (RF) transmitter to communicate between the laptop and the satellites. The SPHERES position and attitude determination system (PADS) uses a combination of infrared (IR) flash, to 1 synchronize their clocks, and ultrasonic time-of- with the third on 14P. The SPHERES hardware flight measurements to triangulate their position was de-manifested from 13P, and then from 14P; in a pseudo-GPS system. The SPHERES the hardware was returned to MIT in November satellites operate within an approximately 2m by 2003. NASA’s objective was to maximize 2m by 2m volume [1]. science with minimum mass. The SPHERES team had multiple iterations of manifest SPHERES satellites run on CO2 propellant at 25 opportunities over the next three years in order to psi, for an effective Isp of 32 seconds. The send up partial SPHERES hardware to satellites are powered by two battery packs, accomplish some minimized science objectives. consisting of eight AA batteries each. Each However, none of these opportunities came to satellite also has an expansion port, which allows fruition. The first SPHERES satellite (Red) was for external payloads to be attached at a future launched aboard flight Progress 21P on April date [2]. 24th, 2006. Also launched was a communications transmitter, along with several The ISS configuration is replicated at the MIT batteries and tanks. By 2006, the SPHERES Space Systems Laboratory in Cambridge, MA. team had shrunk from eight to six members, with Three ground satellites are maintained for testing only four original members remaining. of algorithms prior to launch. The first test sessions occurred less than a month 2. SPHERES History after launch, on May 18th and May 20th 2006, operated by Expedition 13 astronaut Jeff SPHERES was originally developed as part of a Williams. The second satellite (Blue) launched undergraduate design class at MIT in 1999. The aboard STS-121 (ULF1.1) on July 4th, 2006. objective was to give undergraduates the The third and final satellite (Orange) launched on experience of the entire lifecycle of the December 10th, 2006 on board STS-116 (12A.1). development of an aerospace product, teaching SPHERES hardware was took four launches to the engineering process as “conceive, design, arrive on the ISS, and over three years longer implement, and operate” (CDIO). Thirteen than the originally assumed few months. undergraduate students worked to develop functional requirements beginning in February Table 1 highlights the test session dates and the 1999, with fully integrated prototype hardware astronaut operating SPHERES. Table 2 gives a ready a year later. The satellites were tested description of all astronauts trained on aboard the KC-135 Reduced Gravity Aircraft in SPHERES, when they trained, and when they the spring of 2000 in short duration microgravity operated SPHERES on the ISS, if applicable. testing. Table 2 shows the time delay between the training and operations for the crew. The design of the CDIO class was updated and the flight satellites were developed, as a joint Table 1: SPHERES Test Session Dates effort with Payload Systems Inc. Three satellites Session Date Exp Crew were scheduled to be delivered to NASA in June TS001 5/18/2006 13 J. Williams 2003, with an expected launch date of July 2003. TS002 5/20/2006 13 J. Williams After the Columbia accident in February 2003, TS003 8/12/2006 13 J. Williams the team projected a delay of a few months. TS004 8/19/2006 13 J. Williams TS005 11/11/2006 14 M. Lopez-Alegria The first SPHERES hardware, consisting of one TS006 3/17/2007 14 S. Williams / M. beacon and beacon tester, was launched on Lopez-Alegria Progress 12P. This was used in Expedition 8 by TS007 3/24/2007 14 S. Williams astronaut Michael Foale to test the ultrasound TS008 4/27/2007 14 S. Williams and infrared environment of the US lab. This activity was performed twice, once in November 2003 and again in March of 2004. Table 2: Crew Training Dates vs Flight Dates Name Expedition Trained On ISS All satellite hardware was delivered in August Mike Barrat N/A July 2002 Dry Run 2003 with the expectation of launch in Mike Foale Exp 8 Oct 2003 November on Progress 13P and January 2004 on 14P. The manifest for 13P was two satellites, 2 Mike Fincke Exp 9 Jan 2004 session. The SPHERES team did not have a Exp 13 B/U Jan 2006 formalized plan from delivery to operations, but Exp 16 B/U May 2007 instead was reactionary and flexible to what the Dan Tani Exp B/U Aug 2004 latest news was from NASA. Through the Exp 16 May 2007 preparation and execution of the first seven test Leroy Chiao Exp 10 Aug 2004 session, a formalized process was developed, Bill McArthur Exp 10 B/U Aug 2005 Exp 12 Mar 2005 executed, and refined. John Phillips Exp 11 Aug 2005 Clay Anderson Exp 11 B/U Mar 2005 3.2 Preparation for Operations Exp 15* May 2006 Preparation for the first test session began Jeff Williams Exp 13 Mar 2005 May 2006 roughly a month prior to session date. The two Suni Williams Exp 13 Mar 2005 Mar 2007 main aspects were algorithm and operations Exp 14* May 2006 preparation. Algorithm preparation consisted Leo Eyhart ESA B/U Apr 2006 of creating the SPHERES Program File (SPF). Thomas Reiter Exp 13 ESA Apr 2006 The SPF file contains the project file with the Mike Lopez- Exp 14 May 2006 Nov 2006 algorithms, html files for an overview of each Alegria test, and a text file to link the tests from the Peggy Whitson Exp 13 May 2006 graphical user interface (GUI) to a test command Gregory Exp 15 B/U Dec 2006 to the satellite. The first test session SPF Chamitoff delivery to DOD Space Test Program (STP) was Sandra Exp 17 May 2007 th Mangus on April 28 . * Indicates refresher training Operations preparation included the development 3. Test Session Description of contingency plans and processes for the SPHERES team, practice session on the ground 3.1 Original Concept of Operations with retired astronaut Jeff Hoffman, and a crew The concept of operations during SPHERES conference with astronaut Jeff Williams prior to development, up until the spring of 2006, was the first test session. fairly abstract. The team had requested to be onsite at Johnson Space Center (JSC) for the first For contingency operations, the team employed two test sessions, in order to have live coverage. two methods of preparation, a listing of possible It was assumed that live coverage would only be anomalies with corresponding visual/audio available for the first two sessions, and perhaps symptoms and a flow diagram of possible test for critically important sessions afterwards, such outcomes. The list of possible anomalies was as the first three satellite operations.