Halo orbits are a sub-class of Lissajous orbits. See this answer for (much) more on that.

DSCOVR's orbit will put it in it's Sun Exclusion Zone in about 2020 where the communications line of sight will be too close to the Sun, so there is a planned orbital correction there to handle the situation. You can see from the image the insertion point labeled LOI, and about a dozen cycles in five years. The horizontal and vertical periods are almost the same for this orbit. From Lissajous Orbit Control for the Deep Space Climate Observatory Sun-Earth L1 Libration Point Mission

After 2020, DSCOVR will then have to burn fuel every 3 or 6 months to stay on that exclusion zone-riding ellipse. The linked report predicts that fuel will run out around 2028.

DSCOVR's Lissajous orbit

Question: Why couldn't Triana have her halo orbit, and therefore a much longer continuous-coverage life? Why is DSCOVR in a Lissajous orbit instead of a halo orbit (to stay out of Sun exclusion zone)?

There is relevant discussion in answers and especially comments associated with Why would a mission to Sun-Earth L1 have an instantaneous launch window?

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    $\begingroup$ Larger fuel consumption needed for halo than Lissajous, I am guessing. Wind recently (~June, August, and November of 2020) had to do three maneuvers to put it into a halo instead of a Lissajous orbit to avoid the solar exclusion zone. But Wind was also sitting on ~120 years of remaining fuel, so fuel wasn't the big concern. DSCOVR is not in that same boat. $\endgroup$ – honeste_vivere Feb 22 at 23:06
  • $\begingroup$ @honeste_vivere okay we're making progress. JWST's halo orbit has an expected delta-v budget of only 2.4 m/s per year, but it has an aggressive monitor/correction cadence of two weeks and a giant solar sail that can be used to advantage. 1, 2, 3, 4 $\endgroup$ – uhoh Feb 23 at 3:00
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    $\begingroup$ Oh sorry, no the maneuvers to maintain a halo orbit are not bad, it's the insertion that is problematic. The new Wind orbit is not significantly more expensive fuel-wise than the old Lissajous orbit. However, insertion into the halo orbit from the Lissajous cost us ~40+ m/s of delta-v (whereas typical station keeping maneuvers only cost ~4 cm/s). $\endgroup$ – honeste_vivere Feb 23 at 14:18
  • $\begingroup$ @honeste_vivere related but not completely answered: Why would a mission to Sun-Earth L1 have an instantaneous launch window? $\endgroup$ – uhoh Feb 24 at 1:57

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