Asynchronous Real-time Systems

A goal of the Iligl)t Sys(cm ‘[ ’cs(bd (1 ’S’1 ’ ) is 10 gcmrdlim and opt im im system-level spacecraft in[crfaccs in suppor( of mpid prototypit~g a n d intcgta[ion testins [ l;S’l’, [’194]. Using software 10 simulate the spacccrdft and environment al arbitrary levels of abstraction is lhc Illcmc oftbis paper. A snapshot of a spacccmfi under clcvclopmmt includes a combination o f barciwarc caginecring 1I1O(ICIS, brcadboads, brass boards, and soflwarc simulations. ‘1’hc l;S”l’ clcvclopmenl env i ronment iaclLdcs Icchniqocs h tbc smodb rcplaccmcnt d s o f t w a r e simalalicms w i th hardware or flight software as it bccomcs avail ab]c. ‘Ill is facilitates cmnplcx Ilarcl}varc-it] -tllcImp sinlulalions. 1 n part ica]ar, an arch itcct Llre was clevclopcd to suppml rapid protolypiag of plaac(ary spacecraft systems. ‘1’his involves cncapsalating core m-boarcl services rcqLtircd of any spacccrdfi (pointing, command handling, tclemc[ry sloragc, cIc.) and simulating a flight-like crlvironmcat, Silualalitlg Ihc motion of a spacecraft or the output of a camera in real-tilnc is a substantial task. OLIr appmacb is to mllcct ancl integrate simulation syslcms that mdcl the in-flight c.nvim)mcnt, (hlr silnalatioa architcc[urc is a layered ball’s-eye, or onion pal[crm tcminisccat of t r a d i t i o n a l unipmccsscw opcra[ing syslcm cksiga [’I’an87]. “1’hc center is the syskm uadcr test. ‘1’hc first Iaycr oat is tbc intcrfacc clrivcr layer. ‘[’his sbadcd layer presents services to the core systcm t h a t w i l l remain coaslaat a s oatcr layer silnolatioas arc replaced with real clcvices. I;or example, ia f:igLlre 1 the core cock tinclcr test might bc a spacecraft a[ti~LldC COlltI’01 SyStCIH, ancl tbc first Iaycr oLIl m i g h t provicie tbc core system with a gyro_ get.. state ( ) fLinctioa that is inilially implemented as a mnotc proccdLIrc cal I (KIT) to a real-time dynamics moclcl sialLllating spacecraft motion. “1’11 is fLlnction might later bc implemented to send a message across a bLls to spacccrafi rate sensors.