!25 · krz/moonrise

App/Sources/MarsSection.swift added +28

		@@ -0,0 +1,28 @@
	1	import SkyEngine
	2	import SwiftUI
	3
	4	/// Local mean solar time and sol number at the active Mars rovers, ticking each second.
	5	struct MarsSection: View {
	6	var body: some View {
	7	VStack(alignment: .leading, spacing: 10) {
	8	Text("Mars now").font(.caption2.weight(.medium)).textCase(.uppercase).tracking(0.8).dimmed(0.6)
	9	TimelineView(.periodic(from: .now, by: 1)) { ctx in
	10	VStack(alignment: .leading, spacing: 8) {
	11	ForEach(MarsTime.Rover.active) { rover in
	12	HStack(alignment: .firstTextBaseline) {
	13	VStack(alignment: .leading, spacing: 2) {
	14	Text(rover.name).font(.subheadline.weight(.medium))
	15	Text("\(rover.site) · sol \(MarsTime.sol(ctx.date, rover: rover))").font(.footnote).dimmed(0.7)
	16	}
	17	Spacer()
	18	Text(MarsTime.format(hours: MarsTime.localMeanTime(ctx.date, eastLongitude: rover.longitude)))
	19	.font(.title3.monospacedDigit())
	20	}
	21	.accessibilityElement(children: .combine)
	22	}
	23	}
	24	}
	25	Text("Local mean solar time. A Mars sol is 24 h 39 m 35 s.").font(.caption2).dimmed(0.5)
	26	}
	27	}
	28	}

App/Sources/SystemScreen.swift +1

		@@ -88,6 +88,7 @@ struct SystemScreen: View {
88	88	}
89	89	}
90	90	DSNSection(ink: ink, accent: accent).padding(.top, 24)
	91	MarsSection().padding(.top, 24)
91	92	Text("Spacecraft positions: NASA/JPL Horizons. Pioneer 10 and 11 positions after contact was lost are predictions.")
92	93	.font(.caption2).dimmed(0.5).padding(.vertical, 16)
93	94	}

Packages/MoonriseKit/Sources/SkyEngine/MarsTime.swift added +45

		@@ -0,0 +1,45 @@
	1	import Foundation
	2
	3	/// Mars Coordinated Time and rover local times, after NASA GISS Mars24 (Allison & McEwen 2000).
	4	public enum MarsTime {
	5	public struct Rover: Sendable, Identifiable {
	6	public var name: String
	7	public var site: String
	8	/// East longitude in degrees.
	9	public var longitude: Double
	10	/// Mars Sol Date of the landing sol's local midnight (sol 0).
	11	public var landingSol: Int
	12	public var id: String { name }
	13
	14	public static let active: [Rover] = [
	15	Rover(name: "Perseverance", site: "Jezero Crater", longitude: 77.45, landingSol: 52304),
	16	Rover(name: "Curiosity", site: "Gale Crater", longitude: 137.44, landingSol: 49269),
	17	]
	18	}
	19
	20	/// TT − UTC: 32.184 s plus 37 leap seconds (none since 2017).
	21	static let ttMinusUTC = 69.184
	22
	23	/// Mars Sol Date.
	24	public static func msd(_ date: Date) -> Double {
	25	let jdTT = (date.timeIntervalSince1970 + ttMinusUTC) / 86_400 + 2_440_587.5
	26	return (jdTT - 2_405_522.0028779) / 1.0274912517
	27	}
	28
	29	/// Local mean solar time in hours (0..<24) at an east longitude.
	30	public static func localMeanTime(_ date: Date, eastLongitude: Double) -> Double {
	31	let mtc = (msd(date) * 24).truncatingRemainder(dividingBy: 24)
	32	let t = (mtc + eastLongitude / 15).truncatingRemainder(dividingBy: 24)
	33	return t < 0 ? t + 24 : t
	34	}
	35
	36	/// Mission sol number (sol 0 is the landing sol).
	37	public static func sol(_ date: Date, rover: Rover) -> Int {
	38	Int((msd(date) + rover.longitude / 360).rounded(.down)) - rover.landingSol
	39	}
	40
	41	public static func format(hours: Double) -> String {
	42	let total = Int(hours * 60)
	43	return String(format: "%02d:%02d", total / 60 % 24, total % 60)
	44	}
	45	}

Packages/MoonriseKit/Tests/SkyEngineTests/MarsTimeTests.swift added +24

		@@ -0,0 +1,24 @@
	1	import Foundation
	2	import Testing
	3	@testable import SkyEngine
	4
	5	@Test func msdReferenceEpoch() {
	6	// Allison & McEwen (2000): MSD 44796.0 at about 2000-01-06 00:00 TT.
	7	let tt = Date(timeIntervalSince1970: 947_116_800 - 69.184)
	8	#expect(abs(MarsTime.msd(tt) - 44796.0) < 0.001)
	9	}
	10
	11	@Test func landingDaysAreSolZero() throws {
	12	let perseverance = try #require(MarsTime.Rover.active.first { $0.name == "Perseverance" })
	13	let curiosity = try #require(MarsTime.Rover.active.first { $0.name == "Curiosity" })
	14	#expect(MarsTime.sol(utc("2021-02-18T20:55:00Z"), rover: perseverance) == 0)
	15	#expect(MarsTime.sol(utc("2012-08-06T05:17:57Z"), rover: curiosity) == 0)
	16	// One sol is 88,775.244 s.
	17	#expect(MarsTime.sol(utc("2021-02-18T20:55:00Z").addingTimeInterval(88_775.244), rover: perseverance) == 1)
	18	}
	19
	20	@Test func localTimeIsWithinADay() {
	21	let t = MarsTime.localMeanTime(.now, eastLongitude: 77.45)
	22	#expect(t >= 0 && t < 24)
	23	#expect(MarsTime.format(hours: 13.5) == "13:30")
	24	}

v2: Mars local time !25