// Check that the small body has the right degrees of freedom in the frame of // the big body. TEST_F(BodyCentredNonRotatingDynamicFrameTest, SmallBodyInBigFrame) { int const steps = 100; Bivector<double, ICRFJ2000Equator> const axis({0, 0, 1}); RelativeDegreesOfFreedom<ICRFJ2000Equator> const initial_big_to_small = small_initial_state_ - big_initial_state_; ContinuousTrajectory<ICRFJ2000Equator>::Hint hint; for (Instant t = t0_; t < t0_ + 1 * period_; t += period_ / steps) { DegreesOfFreedom<ICRFJ2000Equator> const small_in_inertial_frame_at_t = solar_system_.trajectory(*ephemeris_, small). EvaluateDegreesOfFreedom(t, &hint); auto const rotation_in_big_frame_at_t = Rotation<ICRFJ2000Equator, Big>(2 * π * (t - t0_) * Radian / period_, axis, DefinesFrame<Big>{}); DegreesOfFreedom<Big> const small_in_big_frame_at_t( rotation_in_big_frame_at_t(initial_big_to_small.displacement()) + Big::origin, rotation_in_big_frame_at_t(initial_big_to_small.velocity())); auto const to_big_frame_at_t = big_frame_->ToThisFrameAtTime(t); EXPECT_THAT(AbsoluteError( to_big_frame_at_t(small_in_inertial_frame_at_t).position(), small_in_big_frame_at_t.position()), Lt(0.3 * Milli(Metre))); EXPECT_THAT(AbsoluteError( to_big_frame_at_t(small_in_inertial_frame_at_t).velocity(), small_in_big_frame_at_t.velocity()), Lt(4 * Milli(Metre) / Second)); } }
TEST_F(BodyCentredNonRotatingDynamicFrameTest, GeometricAcceleration) { int const steps = 10; RelativeDegreesOfFreedom<ICRFJ2000Equator> const initial_big_to_small = small_initial_state_ - big_initial_state_; Length const big_to_small = initial_big_to_small.displacement().Norm(); Acceleration const small_on_big = small_gravitational_parameter_ / (big_to_small * big_to_small); for (Length y = big_to_small / steps; y < big_to_small; y += big_to_small / steps) { Position<Big> const position(Big::origin + Displacement<Big>({0 * Kilo(Metre), y, 0 * Kilo(Metre)})); Acceleration const big_on_position = -big_gravitational_parameter_ / (y * y); Acceleration const small_on_position = small_gravitational_parameter_ / ((big_to_small - y) * (big_to_small - y)); Vector<Acceleration, Big> const expected_acceleration( {0 * SIUnit<Acceleration>(), small_on_position + big_on_position - small_on_big, 0 * SIUnit<Acceleration>()}); EXPECT_THAT(AbsoluteError( big_frame_->GeometricAcceleration( t0_, DegreesOfFreedom<Big>(position, Velocity<Big>())), expected_acceleration), Lt(1e-10 * SIUnit<Acceleration>())); } }
TEST_F(TimeScalesTest, UT1Continuity) { // Continuity with TAI. We have a fairly low resolution for UT1 at that time, // as well as high errors (~20 ms), and TAI was synchronized with UT2 anyway, // so it's not going to get much better than 100 ms. EXPECT_THAT( AbsoluteError("1958-01-01T00:00:00"_UT1, "1958-01-01T00:00:00"_TAI), Lt(100 * Milli(Second))); // Continuity at the beginning of the EOP C02 series. EXPECT_THAT(AbsoluteError("1961-12-31T23:59:59,000"_UT1, "1961-12-31T23:59:58,967"_UTC), Lt(0.5 * Milli(Second))); EXPECT_THAT(AbsoluteError("1962-01-01T00:00:00,000"_UT1, "1961-12-31T23:59:59,967"_UTC), Lt(0.5 * Milli(Second))); EXPECT_THAT(AbsoluteError("1962-01-01T00:00:00,033"_UT1, "1962-01-01T00:00:00,000"_UTC), Lt(0.5 * Milli(Second))); EXPECT_THAT(AbsoluteError("1962-01-01T00:00:01,033"_UT1, "1962-01-01T00:00:01,000"_UTC), Lt(0.5 * Milli(Second))); // Continuity across a stretchy UTC leap. EXPECT_THAT(AbsoluteError("1964-03-31T23:59:59,000"_UT1, "1964-03-31T23:59:59,160"_UTC), Lt(0.5 * Milli(Second))); EXPECT_THAT(AbsoluteError("1964-03-31T23:59:59,900"_UT1, "1964-03-31T23:59:60,060"_UTC), Lt(0.5 * Milli(Second))); EXPECT_THAT(AbsoluteError("1964-03-31T23:59:59,940"_UT1, "1964-04-01T00:00:00,000"_UTC), Lt(0.5 * Milli(Second))); EXPECT_THAT(AbsoluteError("1964-04-01T00:00:00,000"_UT1, "1964-04-01T00:00:00,060"_UTC), Lt(0.5 * Milli(Second))); }
// Check the times of the lunar eclipses in LunarEclipseTest. TEST_F(TimeScalesTest, LunarEclipses) { EXPECT_THAT(AbsoluteError("1950-04-02T20:44:34.0"_TT, "1950-04-02T20:44:04.8"_UT1), Lt(14 * Milli(Second))); EXPECT_THAT(AbsoluteError("1950-04-02T20:49:16.7"_TT, "1950-04-02T20:48:47.5"_UT1), Lt(14 * Milli(Second))); EXPECT_THAT(AbsoluteError("1950-09-26T04:17:11.4"_TT, "1950-09-26T04:16:42.1"_UT1), Lt(86 * Milli(Second))); EXPECT_THAT(AbsoluteError("1950-09-26T04:21:55.5"_TT, "1950-09-26T04:21:26.1"_UT1), Lt(15 * Milli(Second))); EXPECT_THAT(AbsoluteError("1951-03-23T10:37:33.2"_TT, "1951-03-23T10:37:03.7"_UT1), Lt(92 * Milli(Second))); EXPECT_THAT(AbsoluteError("1951-03-23T10:50:16.8"_TT, "1951-03-23T10:49:47.3"_UT1), Lt(92 * Milli(Second))); EXPECT_THAT(AbsoluteError("1951-09-15T12:27:06.3"_TT, "1951-09-15T12:26:36.6"_UT1), Lt(99 * Milli(Second))); EXPECT_THAT(AbsoluteError("1951-09-15T12:38:51.5"_TT, "1951-09-15T12:38:21.8"_UT1), Lt(99 * Milli(Second))); EXPECT_THAT(AbsoluteError("1952-02-11T00:28:39.9"_TT, "1952-02-11T00:28:10.0"_UT1), Lt(69 * Milli(Second))); EXPECT_THAT(AbsoluteError("1952-02-11T00:39:47.6"_TT, "1952-02-11T00:39:17.7"_UT1), Lt(69 * Milli(Second))); EXPECT_THAT(AbsoluteError("1952-08-05T19:40:29.4"_TT, "1952-08-05T19:39:59.3"_UT1), Lt(57 * Milli(Second))); EXPECT_THAT(AbsoluteError("1952-08-05T19:47:54.8"_TT, "1952-08-05T19:47:24.7"_UT1), Lt(57 * Milli(Second))); EXPECT_THAT(AbsoluteError("2000-01-21T04:41:30.5"_TT, "2000-01-21T04:40:26.7"_UT1), Lt(45 * Milli(Second))); EXPECT_THAT(AbsoluteError("2000-01-21T04:44:34.5"_TT, "2000-01-21T04:43:30.6"_UT1), Lt(56 * Milli(Second))); EXPECT_THAT("2048-01-01T06:53:54.8"_TT - "2048-01-01T06:52:23.6"_TT, AlmostEquals(91.2 * Second, 3e6, 4e6)); EXPECT_THAT("2048-01-01T06:58:19.8"_TT - "2048-01-01T06:56:48.6"_TT, AlmostEquals(91.2 * Second, 3e6, 4e6)); }
// See the list of steps at // https://hpiers.obspm.fr/iers/bul/bulc/TimeSteps.history. // Note that while the same file is used to check that the date string is valid // with respect to positive or negative leap seconds, the actual conversion is // based exclusively on https://hpiers.obspm.fr/iers/bul/bulc/UTC-TAI.history, // so this provides some sort of cross-checking. TEST_F(TimeScalesTest, StretchyLeaps) { EXPECT_THAT(AbsoluteError("1961-07-31T24:00:00,000"_UTC - 0.050 * Second, "1961-07-31T23:59:59,900"_UTC), Lt(1 * Micro(Second))); EXPECT_THAT( AbsoluteError("1961-08-01T00:00:00"_UTC, "1961-08-01T00:00:01,648"_TAI), Lt(0.5 * Milli(Second))); EXPECT_THAT(AbsoluteError("1963-10-31T24:00:00,000"_UTC - 0.100 * Second, "1963-10-31T23:59:60,000"_UTC), Lt(1 * Micro(Second))); EXPECT_THAT( AbsoluteError("1963-11-01T00:00:00"_UTC, "1963-11-01T00:00:02,697"_TAI), Lt(0.5 * Milli(Second))); EXPECT_THAT(AbsoluteError("1964-03-31T24:00:00,000"_UTC - 0.100 * Second, "1964-03-31T23:59:60,000"_UTC), Lt(1 * Micro(Second))); EXPECT_THAT( AbsoluteError("1964-04-01T00:00:00"_UTC, "1964-04-01T00:00:02,984"_TAI), Lt(0.5 * Milli(Second))); EXPECT_THAT(AbsoluteError("1964-08-31T24:00:00,000"_UTC - 0.100 * Second, "1964-08-31T23:59:60,000"_UTC), Lt(1 * Micro(Second))); EXPECT_THAT( AbsoluteError("1964-09-01T00:00:00"_UTC, "1964-09-01T00:00:03,282"_TAI), Lt(0.5 * Milli(Second))); EXPECT_THAT(AbsoluteError("1964-12-31T24:00:00,000"_UTC - 0.100 * Second, "1964-12-31T23:59:60,000"_UTC), Lt(1 * Micro(Second))); EXPECT_THAT( AbsoluteError("1965-01-01T00:00:00"_UTC, "1965-01-01T00:00:03,540"_TAI), Lt(0.5 * Milli(Second))); EXPECT_THAT(AbsoluteError("1965-02-28T24:00:00,000"_UTC - 0.100 * Second, "1965-02-28T23:59:60,000"_UTC), Lt(1 * Micro(Second))); EXPECT_THAT( AbsoluteError("1965-03-01T00:00:00"_UTC, "1965-03-01T00:00:03,717"_TAI), Lt(0.5 * Milli(Second))); EXPECT_THAT(AbsoluteError("1965-06-30T24:00:00,000"_UTC - 0.100 * Second, "1965-06-30T23:59:60,000"_UTC), Lt(1 * Micro(Second))); EXPECT_THAT( AbsoluteError("1965-07-01T00:00:00"_UTC, "1965-07-01T00:00:03,975"_TAI), Lt(0.5 * Milli(Second))); EXPECT_THAT(AbsoluteError("1965-08-31T24:00:00,000"_UTC - 0.100 * Second, "1965-08-31T23:59:60,000"_UTC), Lt(1 * Micro(Second))); EXPECT_THAT( AbsoluteError("1965-09-01T00:00:00"_UTC, "1965-09-01T00:00:04,155"_TAI), Lt(0.5 * Milli(Second))); EXPECT_THAT(AbsoluteError("1968-01-31T24:00:00,000"_UTC - 0.100 * Second, "1968-01-31T23:59:59,800"_UTC), Lt(1 * Micro(Second))); EXPECT_THAT( AbsoluteError("1968-02-01T00:00:00"_UTC, "1968-02-01T00:00:06,186"_TAI), Lt(0.5 * Milli(Second))); EXPECT_THAT(AbsoluteError("1971-12-31T24:00:00,000"_UTC - 0.107'7580 * Second, "1971-12-31T23:59:60,000"_UTC), Lt(1 * Micro(Second))); EXPECT_THAT( AbsoluteError("1972-01-01T00:00:00"_UTC, "1972-01-01T00:00:10,000"_TAI), Lt(0.5 * Milli(Second))); }