Conjunctions (TOLEOS)

Conjunctions (TOLEOS)#

SERVER_URL = "https://vires.services/ows"

%load_ext watermark
%watermark -i -v -p viresclient,pandas,xarray,matplotlib,cartopy

Python implementation: CPython
Python version       : 3.11.6
IPython version      : 8.18.0

viresclient: 0.14.1
pandas     : 2.1.3
xarray     : 2023.12.0
matplotlib : 3.8.2
cartopy    : 0.22.0

import datetime as dt

import matplotlib.pyplot as plt
import numpy as np
from viresclient import SwarmRequest

Product information#

The MM_OPER_CON_EPH_2_ product contains conjunction information between Swarm (A, B, C), CHAMP, GOCE, GRACE (1, 2), and GRACE-FO (1, 2).

The product is implemented in VirES as two collections, each available as a single flat time series.

MM_OPER_CON_EPH_2_:crossover contains the list of times where satellite ground-tracks overlap within a ~7 hour window.

MM_OPER_CON_EPH_2_:plane_alignment contains much rarer events, where the planes of different spacecraft are aligned

request = SwarmRequest(SERVER_URL)
for collection in ("MM_OPER_CON_EPH_2_:crossover", "MM_OPER_CON_EPH_2_:plane_alignment"):
    print(f"{collection}:\n{request.available_measurements(collection)}\n")

MM_OPER_CON_EPH_2_:crossover:
['time_1', 'time_2', 'time_difference', 'satellite_1', 'satellite_2', 'latitude', 'longitude', 'altitude_1', 'altitude_2', 'magnetic_latitude', 'magnetic_longitude', 'local_solar_time_1', 'local_solar_time_2']

MM_OPER_CON_EPH_2_:plane_alignment:
['time', 'altitude_1', 'altitude_2', 'ltan_1', 'ltan_2', 'ltan_rate_1', 'ltan_rate_2', 'satellite_1', 'satellite_2']

Fetching data#

Crossovers#

Let’s fetch all the available conjunctions for a given day.

Note that the start_time and end_time specified are used for a full interval query over both time_1 and time_2 given in the outputs.

request = SwarmRequest(SERVER_URL)
request.set_collection("MM_OPER_CON_EPH_2_:crossover")
request.set_products(
    request.available_measurements("MM_OPER_CON_EPH_2_:crossover")
)
data = request.get_between(
    dt.datetime(2020, 1, 1),
    dt.datetime(2020, 1, 2),
)
df = data.as_dataframe()
df

	altitude_1	longitude	Spacecraft	time_2	altitude_2	satellite_2	magnetic_latitude	latitude	magnetic_longitude	local_solar_time_1	time_difference	satellite_1	local_solar_time_2
time_1
2019-12-31 16:45:34.507031296	508386.037694	-168.631028	-	2020-01-01 00:03:20.865398528	445802.184339	SWC	79.949318	87.321728	-164.456295	12.813727	26266.358365	GF1	5.517517
2019-12-31 16:45:34.666273280	508384.174138	-168.540829	-	2020-01-01 00:03:29.977781248	445817.275119	SWA	79.956628	87.330964	-164.497178	12.822272	26275.311505	GF1	5.523574
2019-12-31 16:45:58.498234368	508285.501449	-168.714116	-	2020-01-01 00:03:20.801171712	445802.184832	SWC	79.946058	87.322763	-164.469981	12.808170	26242.302943	GF2	5.518642
2019-12-31 16:45:58.642820352	508283.850034	-168.645621	-	2020-01-01 00:03:29.901976576	445817.254541	SWA	79.952162	87.331274	-164.509020	12.815265	26251.259161	GF2	5.523248
2019-12-31 17:32:44.852499968	522002.918063	-0.411375	-	2020-01-01 00:50:00.517710848	464173.845073	SWC	-79.455668	-87.324172	14.152966	0.806052	26235.665210	GF1	17.518367
...	...	...	...	...	...	...	...	...	...	...	...	...	...
2020-01-01 23:42:29.863429888	511607.216872	38.339964	-	2020-01-02 01:49:40.551429632	508318.284479	GF1	75.124965	81.399341	146.831766	4.383929	7630.688001	SWB	2.264293
2020-01-01 23:43:26.628039168	511293.312109	42.564400	-	2020-01-02 03:59:58.525515520	445127.722214	SWA	71.743591	77.902092	142.500846	6.837217	15391.897473	SWB	2.561690
2020-01-01 23:43:39.701632768	511208.234498	43.203973	-	2020-01-02 03:59:37.480210944	445042.331540	SWC	70.954621	77.089844	141.708566	6.874009	15357.778578	SWB	2.607960
2020-01-01 23:59:39.406749952	507422.300094	59.698567	-	2020-01-02 02:11:45.781679616	435473.994296	SWC	14.544932	21.148917	134.574062	6.175955	7926.374931	GF2	3.974184
2020-01-01 23:59:59.915086080	507614.183522	59.668240	-	2020-01-02 02:12:29.624203264	435703.475318	SWC	17.345313	23.980608	134.913629	6.186112	7949.709113	GF1	3.977859

5408 rows × 13 columns

Pairs of conjunctioning spacecraft are defined with short designations in the satellite_1 and satellite_2 variables:

df["satellite_1"].unique()

array(['GF1', 'GF2', 'SWB', 'SWC', 'SWA'], dtype=object)

df["satellite_2"].unique()

array(['SWC', 'SWA', 'SWB', 'GF2', 'GF1'], dtype=object)

Each conjunction has a start and end time defined with the time_1 and time_2 variables:

df.iloc[0:5][["time_2", "satellite_1", "satellite_2"]]

	time_2	satellite_1	satellite_2
time_1
2019-12-31 16:45:34.507031296	2020-01-01 00:03:20.865398528	GF1	SWC
2019-12-31 16:45:34.666273280	2020-01-01 00:03:29.977781248	GF1	SWA
2019-12-31 16:45:58.498234368	2020-01-01 00:03:20.801171712	GF2	SWC
2019-12-31 16:45:58.642820352	2020-01-01 00:03:29.901976576	GF2	SWA
2019-12-31 17:32:44.852499968	2020-01-01 00:50:00.517710848	GF1	SWC

We can select all the conjunctions containing a given satellite:

df_SWA = df.where((df["satellite_1"] == "SWA")|(df["satellite_2"] == "SWA")).dropna()
df_SWA

	altitude_1	longitude	Spacecraft	time_2	altitude_2	satellite_2	magnetic_latitude	latitude	magnetic_longitude	local_solar_time_1	time_difference	satellite_1	local_solar_time_2
time_1
2019-12-31 16:45:34.666273280	508384.174138	-168.540829	-	2020-01-01 00:03:29.977781248	445817.275119	SWA	79.956628	87.330964	-164.497178	12.822272	26275.311505	GF1	5.523574
2019-12-31 16:45:58.642820352	508283.850034	-168.645621	-	2020-01-01 00:03:29.901976576	445817.254541	SWA	79.952162	87.331274	-164.509020	12.815265	26251.259161	GF2	5.523248
2019-12-31 17:32:44.934890496	522004.159533	-0.365544	-	2020-01-01 00:50:09.627804672	464161.845406	SWA	-79.460015	-87.328937	14.136825	0.811638	26244.692912	GF1	17.521446
2019-12-31 17:33:08.975226624	522106.188666	-0.498389	-	2020-01-01 00:50:09.531093760	464161.901037	SWA	-79.454945	-87.329375	14.116901	0.802755	26220.555867	GF2	17.519267
2019-12-31 17:42:18.655843840	511774.213962	120.426718	-	2020-01-01 00:02:09.084413952	445697.680298	SWA	75.269785	84.623616	-175.176848	8.064305	22790.428566	SWB	1.733630
...	...	...	...	...	...	...	...	...	...	...	...	...	...
2020-01-01 23:31:37.199038976	524464.926293	54.144711	-	2020-01-02 00:10:47.848054528	463967.092769	SWA	-82.426605	-85.252281	30.386096	3.789605	2350.649018	GF2	3.136647
2020-01-01 23:36:50.826312448	511401.685124	-115.750956	-	2020-01-02 00:59:48.513515776	445355.973591	SWA	80.903810	76.710613	-87.255342	17.280079	4977.687203	SWB	15.897388
2020-01-01 23:41:14.676492288	511872.512023	21.364816	-	2020-01-02 07:08:49.337390592	445591.642678	SWA	79.420521	85.793936	156.361396	8.571359	26854.660897	SWB	1.111731
2020-01-01 23:41:47.813570304	511777.132307	31.918781	-	2020-01-02 05:34:56.224296704	445578.775959	SWA	77.564465	83.922645	151.398185	7.710203	21188.410732	SWB	1.824534
2020-01-01 23:43:26.628039168	511293.312109	42.564400	-	2020-01-02 03:59:58.525515520	445127.722214	SWA	71.743591	77.902092	142.500846	6.837217	15391.897473	SWB	2.561690

1657 rows × 13 columns

Plane alignments#

request = SwarmRequest(SERVER_URL)
request.set_collection("MM_OPER_CON_EPH_2_:plane_alignment")
request.set_products(
    request.available_measurements("MM_OPER_CON_EPH_2_:plane_alignment")
)
data = request.get_between(
    dt.datetime(2000, 1, 1),
    dt.datetime(2022, 1, 1),
)
df = data.as_dataframe()
df

	ltan_rate_1	altitude_1	Spacecraft	ltan_2	ltan_1	altitude_2	satellite_2	ltan_rate_2	satellite_1
time
2003-05-11 10:10:03.145992192	-0.091268	400547.265815	-	4.684153	16.684153	488291.762308	GR2	-0.074543	CH
2003-05-11 10:21:36.896242176	-0.091268	400527.975912	-	4.683406	16.683406	487617.059444	GR1	-0.074549	CH
2005-04-08 16:07:15.667320192	-0.091834	361914.544690	-	0.629215	0.629215	469993.893995	GR2	-0.074332	CH
2005-04-08 16:12:54.103234304	-0.091834	361913.083670	-	0.628855	0.628855	470666.606845	GR1	-0.074331	CH
2007-02-14 05:07:14.704273408	-0.092207	350444.851771	-	22.255276	10.255276	481552.511743	GR2	-0.074526	CH
...	...	...	...	...	...	...	...	...	...
2020-05-21 19:46:01.686648320	-0.089979	436300.307971	-	17.434235	17.434235	485113.048217	GF2	-0.074638	SWC
2020-05-21 20:03:47.512773632	-0.089979	436330.337154	-	17.433122	17.433122	485000.585092	GF1	-0.074633	SWC
2021-09-30 18:39:55.482117120	-0.089902	430877.890053	-	20.642289	20.642289	430878.908792	SWC	-0.090034	SWA
2021-10-03 13:41:11.625304576	-0.085605	503359.670523	-	20.390555	8.390555	431177.812782	SWC	-0.090089	SWB
2021-10-03 15:03:35.963726592	-0.089954	431054.450419	-	8.385697	20.385697	503289.814384	SWB	-0.085605	SWA

82 rows × 9 columns

def alignments(df, sat="SWA"):
    return df.where((df["satellite_1"] == sat)|(df["satellite_2"] == sat)).dropna()

sats = ('CH', 'GO', 'GR1', 'GR2', 'GF1', 'GF2', 'SWA', 'SWB', 'SWC')
fig, axes = plt.subplots(len(sats), 1, figsize=(10, 5), sharex=True)
empty = np.empty(df.index.shape)
empty[:] = np.nan
axes[0].plot(df.index, empty)
for sat, ax in zip(sats, axes):
    _df = alignments(df, sat=sat)
    for date in _df.index:
        ax.axvline(date)
    ax.set_yticks([])
    ax.set_ylabel(sat)
fig.subplots_adjust(hspace=0)
fig.suptitle("Plane alignments");

../_images/bb2021821a89a94b1634bae7fff572115f31c3d6fe92d3320db127854bf75385.png