The Martian environ ment also  poses a seve re ch allenge  to me chani sm d esigners. Th e design survival  temperature s (whi ch in clude margin) f or the RL M’s environm ent span ned fro m -120 to +3 5°C, an d the  qualification operating temperature s were between –60 to +35° C. The  rover d eploy ment sy stem   discu ssed h erein m ust be able to surviv e these extr emes ove r the 20 “sol s” (Martian d ays) over which   stand up may occur im medi ately after lan ding. Some moto rs on th e rover m ust survive ma ny cycle s from - 105 to +8 ºC ove r the missi on’s de sign lifetime,  90 sols. Ad ditionally, be yond the a nticipate d high  temperature durin g the mi ssion, was th e adde d necessity to red uce biologi cally active con tamination t o  levels ben eath those set by Planetary Protectio n enginee rs. Mo st mechani sms engin eers on the MER   met this re quireme nt by b aking their devices to +110°C for 50 hours pri or to final i ntegration with th e  spacecraft. Mechani sms had to survive not only rout ine la unch vibration, but also the i mpact load up to  approximatel y 49 g that  would be expe rienced upon landin g with t he di stinctive airba g cushioning syste m  develop ed at JPL. As will b e discu ssed, gale s of dust particl es we re anticip ated upon landing and during  intermittent d ust sto rms aft er landi ng. 

Figure 2 shows the e ssentials of the stan dup seque nce co mprising t he last of the missi on-critical  deployme nts and ap proximately when th ey occur. Fig ure 4 shows the re st of the  sequ ence with a se ries  of snap shots from the com puter mo del. The fun ctional requi reme nts on the RLM  throug hout this p rocess  were as  follows :   

1. Lift the rover and su spension system far enough to allow the front whe els to cle ar the base p etal  (the plate to which the Ro ver wa s sto wed) when t hey fully deployed. We d esigned to an a rbitrary  value, 75 m m, whi ch proved to be a dequate i n all our te sts. T he time allo cated to this fun ction  was 15 minut es.  2. Cause the rocker-bri dge latch pivot, th e jun cture between  forwa rd and aft su spen sion, to  rotate  throug h a mi nimum an gle of 42 deg rees. (Thi s angle was estim ated to be a bout 39.5 deg rees at   the begin ning of the proj ect. It was ident ified as o ne of the poorly u nderstoo d require ment s, as it  depe nded  on the d evelopment of th e rocker-b ridge latch). T he corre sponding li near stroke  requi rement gre w to about  244 mm (in cluding 2 1 mm margi n). 

At this point, the front ro ckers a nd whe els rotate  through thei r own depl oyme nt range of a pproxim ately  180°. T his is accompli shed throu gh a series of mo tions shared between the wh eel-stee ring a ctuators and  the ro cker deployment a ctuators. Thi s sequence is detaile d in the paper e ntitled “ The chall enge s of  designing th e rocke r-bogie suspension for the Ma rs Exploration Rover”. 

3. Upon reve rsing, allo w the l oose pivot joi nt in re quirem ent (2 ) to latch up at  a fixed angl e. Co ntinue   lowering the  rove r with out interruptio n, wh ile accomm odatin g the fund amentally different  kinem atic rel ationship s of the system. 

Stan dup Part 1 & 2 Raise to HardstopLift Rover Deploy Rockers LowerSol #5 Retract Release Rear Wheels Deploy Bogies Sol #6-7Standup part 3 & 4

Figure 2.  Sequenc e of Rov er standup ev ents  198