Already two weeks into an almost-month-long “window” to reach Mars under the most optimum conditions of planetary alignment and energy expenditure, NASA’s Perseverance rover has the weather gods on its side for an on-time liftoff on Thursday morning. Current predictions, courtesy of the 45th Weather Squadron at Patrick Air Force Base, call for an 80-percent probability of acceptable conditions, with a slight improvement in the event of a 24-hour scrub to Friday. Earlier today (Monday), the mission wrapped up its Launch Readiness Review (LRR) with flying colors. “We are in extraordinary times right now with the coronavirus pandemic,” said NASA Administrator Jim Bridenstine, “and yet we have, in fact, persevered.”
Perseverance will spend 6.5 months in transit to Mars, before it executes a hairy Entry, Descent and Landing (EDL)—guided by a supersonic parachute, rocket-powered SkyCrane and a myriad of other technologies—to alight in the geologically rich Jezero Crater, just north of the Martian equator, on 18 February 2021. It will spend at least one Mars “year”, equivalent to 687 Earth-days, roving an area which might once have harbored a gigantic lake. Assisted by Ingenuity, the first helicopter ever to be deployed on another world, Perseverance will investigate the possible “biosignatures” of past life, collect a “cache” of soil and rock samples to be brought back to Earth on a future sample return mission, evaluate In-Situ Resource Utilization (ISRU) technologies and derive a better understanding of Mars’ dust-driven weather. And according to NASA Associate Administrator Thomas Zurbuchen, speaking earlier today, it carries with it 11 million names of ordinary people, just like you and me. “Because we’re going together,” Dr. Zurbuchen explained, “as a world.”
On Monday, United Launch Alliance (ULA)—whose Atlas V booster will be responsible for delivering Perseverance into deep space for its length cruise to the Red Planet—wrapped up the Launch Readiness Review (LRR). Led by Launch Director Omar Baez of NASA’s Launch Services Program (LSP), this major review of the readiness of the Atlas V, the payload and the mission assets was conducted in the Mission Briefing Room of the Neil Armstrong Operations and Checkout Building at the Kennedy Space Center (KSC) in Florida, and virtually via teleconferencing. At the closure of the meeting, senior leaders were polled and gave a unanimous “Ready Status” for launch, before signing the Launch Readiness Certificate.
“I cannot tell you how thrilled we are to lift Perseverance,” said ULA CEO Tory Bruno. “ULA and its heritage rockets have taken every U.S. mission to Mars, but this one is arguably the most sophisticated and in some ways the most exciting of all of them.”
The launch window for the mission to reach the Red Planet originally extended from 17 July through 11 August, but a number of technical issues including a crane malfunction and contamination concerns forced a slippage to the 30th. Trajectory planners were able to eke out an additional few days in performance time to allow Perseverance to fly as late as 15 August if needed.
“The duration of the daily launch windows varies from day to day,” NASA has previously announced. “The launch windows will last approximately between 30 minutes and two hours, with a unique launch opportunity every five minutes.”
Liftoff from historic Space Launch Complex (SLC)-41 at Cape Canaveral Air Force Station, Fla., on Thursday is scheduled to occur during a two-hour window, which opens at 7:50 a.m. EDT and closes at 9:30 a.m. EDT. “A surface high-pressure ridge will build into South Florida Monday-Tuesday, shifting the pattern and bringing southwest flow with dry mornings and increased storm chances in the afternoon and evenings,” noted the 45th Weather Squadron. This is expected to impinge on the planned 8 a.m. EDT Tuesday rollout of the United Launch Alliance (ULA) Atlas V from the Vertical Integration Facility (VIF) to the SLC-41 pad surface. The 197-foot-tall (60-meter) rocket will ride the quarter-mile (400-meter) distance to the pad atop a Mobile Launch Platform (MLP). “For MLP Roll Day Tuesday, expect increasing chances for a shower or storm around noon as the east coast sea breeze develops and again by late afternoon as inland storms move back east.”
Assuming on-time launch Thursday, Perseverance will rise from Earth less than an hour after local sunrise, promising onlookers a spectacular view of the Atlas V as it powers uphill, under a combined 2.4 million pounds (1.1 million kg) of thrust from the Russian-built RD-180 engine of its Common Core Booster (CCB) and four strap-on solid-fueled rockets. “For launch day Thursday, overall conditions are favorable,” added the 45th, pointing to an 80-percent probability of acceptable weather. “However, an isolated shower just offshore and some mid-level clouds along the coast are likely as a weak front off the coast of the southeast sags southward. Therefore, the primary concerns for launch day are the Cumulus Cloud and Thick Cloud Layer Rules.”
A delay to either Friday or Saturday will produce a slightly different T-0, with the window opening five minutes later at 7:55 a.m. EDT. “For Friday morning, the front weakens, but an isolated shower could still be just offshore,” it was cautioned. With a potential violation of the Cumulus Cloud Rule considered the limiting factor on Friday, conditions on Friday, 31 July, are predicted to be 90-percent-favorable. This is expected to drop back to 80 percent for an attempt on Saturday, 1 August. “For Saturday morning, upper-level winds increase from the east, bringing a slight chance for anvil clouds from any convection over the Gulfstream to move near the Cape,” the 45th concluded. “Therefore, the primary concerns for the 48-hour backup day are the Attached and Detached Anvil Cloud Rules.”