To improve the positioning accuracy of autonomous celestial navigation systems when flying in formation, we exploit the fact that the sole light source in the solar system is the Sun to directly provide positioning information for relative navigation. We term this solar Time Difference of Arrival (TDOA) navigation for formation flying. Solar light has the potential to provide a solar Time of Arrival (TOA) because of its unstable intensity. However, the solar TOA cannot be used for navigation because it has no baseline. To solve this problem, we took the difference between the solar TOAs of two spacecraft (the solar TDOA) as the basis for navigational measurement. The solar TDOA represents the relative distance between two spacecraft in a radial direction. However, whilst the solar TDOA is insensitive to solar direction errors, a free-standing solar TDOA navigation system is not observable. We therefore combined the solar TDOA with the Mars direction and inter-satellite link navigation system, to form an integrated solar TDOA/Mars direction/inter-satellite link navigation method for formation flying. Simulation results indicate that solar TDOA-based integrated navigation for formation flying can provide highly accurate navigation information, especially under relative conditions.

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The effect of the combination of 10-Hydroxycamptothecin (HCPT) and crizotinib (CRI) on EGFR- and KRAS-mutant lung cancer cells was investigated and the conjugates of the two drugs were synthesised. HCPT combined with CRI synergistically inhibited the cell growth and proliferation of H1975, HCC827, and H460 without aggravating adverse effect on the normal cells. The combination synergistically enhanced the cell apoptosis rate through releasing Cyto-C by activation of Bcl-2 family-mediated mitochondrial signalling, which was associate with inactivating of EGFR related downstream signalling pathways including AKT, ERK, JNK, and p38 MAPK. Based on this synergy, the conjugates of HCPT and CRI (compounds CH-1 and CH-2 ) with different chemical bonds were synthesised. Compound CH-1 exhibited stronger cytotoxicity than HCPT and CRI alone or in combination. The combination of HCPT and CRI might be a promising therapeutic regimen and the conjugate CH-1 was a potential target drug for the treatment of lung cancer.